**[NATURAL RESOURCES CONSERVATION SERVICE]{.underline}**

**[CONSERVATION PRACTICE STANDARD]{.underline}**

**[IRRIGATION WATER CONVEYANCE ]{.underline}**

**[DITCH AND CANAL LINING, PLAIN CONCRETE]{.underline}**

**[(Ft]{.underline}[.]{.underline}[)]{.underline}**

**[CODE 428A]{.underline}**

# [DEFINITION]{.underline}

[A fixed lining of impervious material installed in an existing or newly
constructed irrigation field ditch or irrigation canal or
lateral.]{.underline}

# [PURPOSE]{.underline}

[· Improve management of irrigation water]{.underline}

[· Prevent waterlogging of land ]{.underline}

[· Maintain water quality]{.underline}

[· Prevent erosion]{.underline}

[· Reduce water loss]{.underline}

# [CONDITIONS WHERE PRACTICE APPLIES]{.underline}

[Ditches and canals to be lined shall serve as integral parts of an
irrigation water distribution or conveyance system designed to
facilitate the conservation use of soil and water resources on a farm or
group of farms.]{.underline}

[Water supplies and irrigation deliveries for the area served shall be
sufficient to make irrigation practical for the crops to be grown and
the irrigation water application methods to be used.]{.underline}

[Lined ditches and canals shall be located where they are not
susceptible to damage from side drainage flooding, or they shall be
protected from such damage.]{.underline}

[Plain concrete linings shall be installed only in well-drained soils or
on sites where subgrade drainage facilities are installed with or before
the lining. These linings shall not be installed on sites susceptible to
severe frost heave or on sites where experience has indicated that the
sulfate salt concentration in the soil causes rapid deterioration of
concrete.]{.underline}

# [CRITERIA]{.underline}

**[General.]{.underline}**[ Plain concrete linings installed under the
practice standard shall be limited to ditches or canals
with:]{.underline}

[· a bottom width not greater than 6 feet,]{.underline}

[· flow capacity equal to or less than100 cubic feet per second,
and]{.underline}

[· design velocity equal to or less than 15 feet per
second.]{.underline}

**[Materials.]{.underline}**[ On sites where sulfate concentrations
exist, concrete linings may be used only if they are made using special
sulfate-resistant cement in accordance with those shown in Table
1.]{.underline}

[Fly ash can be used to replace up to 15 percent (%) of the cement, by
weight when other pozzolans are not used. ]{.underline}

[Air-entrainment admixture is recommended to improve workability and
reduce damage due to freeze-thaw cycles. In-place, air content shall not
exceed 7% of the volume of concrete.]{.underline}

[Consider the addition of fiber reinforcement to increase durability and
reduce the potential for minor cracking.]{.underline}

[Table 1. Cement Requirements for Concrete Exposed to
Sulfates]{.underline}

  ------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------- ---------------------------------------------------------------
  [Water-soluble sulfate (SO]{.underline}~[4]{.underline}~[) percent by weight]{.underline}   [Sulfate (as SO]{.underline}~[4]{.underline}~[) in water parts per million]{.underline}   [Cement type ASTM C150 or C595]{.underline}
                                                                                                                                                                                        
  [SO]{.underline}~[4]{.underline}[\ ]{.underline}~[ 0]{.underline}                           [SO]{.underline}~[4]{.underline}[\ ]{.underline}~[ 0]{.underline}                         [Any ]{.underline}
  [SO]{.underline}~[4]{.underline}[\ ]{.underline}~[ 0.10]{.underline}                        [SO]{.underline}~[4]{.underline}[\ ]{.underline}~[ 150]{.underline}                       [II, IP(MS), IS(MS), P(MS), I(PM)(MS), I(SM)(MS)]{.underline}
  [SO]{.underline}~[4]{.underline}~[ 0.2]{.underline}                                         [SO]{.underline}~[4]{.underline}~[ 1500]{.underline}                                      [V]{.underline}
                                                                                                                                                                                        
  [SO]{.underline}~[4]{.underline}~[ 2.00]{.underline}                                        [SO]{.underline}~[4]{.underline}~[ 10000]{.underline}                                     [V plus pozzolan]{.underline}^[\*]{.underline}^
                                                                                                                                                                                        
  ------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------- ---------------------------------------------------------------

^[\*]{.underline}^[ Pozzolan known or shown to improve sulfate
resistance in concrete with Type V cement]{.underline}

**[Capacity. ]{.underline}**[A lined ditch or canal shall have enough
capacity to meet its requirement as part of the planned irrigation water
distribution or conveyance system without damage or overtopping. Design
capacity shall be based on the following, whichever is
greater:]{.underline}

[1. The capacity shall be enough to deliver water needed for irrigation
to meet design peak consumptive use of crops.]{.underline}

[2. The capacity shall be enough to provide an adequate irrigation
system for all methods of irrigation planned.]{.underline}

[For design purposes, the capacity shall be considered to be equal to
the capacity as computed by Manning\'s Formula, using a coefficient of
roughness, \"]{.underline}*[n]{.underline}*[\", of not less than
0.015.]{.underline}

**[Velocity.]{.underline}**[ To avoid unstable surge flows, restrict
design velocities in excess of 1.7 times the critical velocity to
straight reaches that discharge into ditch sections or structures
designed to reduce the velocity to less than critical velocity. Maximum
velocity in these straight reaches shall be 15 ft/s.]{.underline}

[The velocity in ditch reaches from which water is to be delivered onto
the field through gates, turnouts, siphon tubes or by similar means
shall be less than supercritical and sufficiently low to permit
operation of the planned takeout structure or device.]{.underline}

**[Freeboard. ]{.underline}**[The required freeboard varies according to
the ditch or canal, velocity of water, horizontal and vertical
alignment, the amount of storm or wastewater that may be intercepted,
and the change in water surface elevation that may occur when any
control structure is operating. The minimum freeboard for any lined
ditch or canal shall be 3 inches (in.) of lining above the design water
surface.]{.underline}

[Minimum freeboard requirement is based on assumption that the finished
channel bottom elevation will vary no more than 0.1 ft from design
elevations. If a construction deviation greater than 0.1 ft is
permitted, the minimum freeboard shall be increased.]{.underline}

[Additional freeboard shall be provided if required by velocity, depth
of flow, alignment, obstruction, curves, and other site
conditions.]{.underline}

**[Water surface elevations. ]{.underline}**[All lined ditches and
canals shall be designed so that water surface elevations at field
takeout points are high enough to provide the required flow onto the
field surface. If ditch checks or other control structures are to be
used to provide necessary head, backwater effect must be considered in
computing freeboard requirements.]{.underline}

[The required elevation of the water surface above the field surface
varies with the type of takeout structure or device used and the amounts
of water to be delivered. A minimum head of 4 in. shall be provided.
Where head is greater than 6 in. and on erosive soils, exit velocity
from gates, turnouts or siphon]{.underline}***[ ]{.underline}***[tubes
may need devices to reduce energy.]{.underline}

**[Lining thickness. ]{.underline}**[Thickness of canal linings must be
established on the basis of engineering consideration on each job.
Location, canal size, velocity, subgrade conditions, method of
construction, operation, and climate shall be evaluated in establishing
thickness to be used. Minimum thickness for plain concrete linings in
rectangular sections shall be 3½ in. For trapezoidal or parabolic
sections, minimum thickness shall be in accordance with Table
2.]{.underline}

[Table 2. --- Minimum required thickness for plain concrete ditch and
canal linings]{.underline}

  ------------------------------------------------------------------------------------ --------------------------------------------------------------------------------------- --------------------
  [Design velocity]{.underline}^[1]{.underline}[\ ]{.underline}^[(ft/s)]{.underline}   [Minimum thickness by climatic area]{.underline}^[2]{.underline}^[ (in.)]{.underline}   
                                                                                                                                                                               
                                                                                       [Warm]{.underline}                                                                      [Cold]{.underline}
                                                                                                                                                                               
  [Less than 9.0]{.underline}                                                          [1.5]{.underline}                                                                       [2.0]{.underline}
  [9.0--12.0 ]{.underline}                                                             [2.5]{.underline}                                                                       [2.5]{.underline}
                                                                                                                                                                               
  [12.0--15.0]{.underline}                                                             [2.5]{.underline}                                                                       [3.0]{.underline}
                                                                                                                                                                               
  ------------------------------------------------------------------------------------ --------------------------------------------------------------------------------------- --------------------

^[1]{.underline}^[Velocities in short chute sections shall not be
considered design velocity.]{.underline}

^[2]{.underline}^[Climatic area:]{.underline}

[Warm -- Average January temperature is 40 °F and above]{.underline}

[Cold -- Average January temperature is less than 40 °F.]{.underline}

**[Ditch or canal side slopes. ]{.underline}**[Plain concrete linings
are generally used in ditches and canals that have either a trapezoidal
or parabolic cross section.]{.underline}

[They may be used in rectangular sections if the sidewall height is not
greater than 1½ ft. Side slopes for usual construction methods shall not
be steeper than shown below:]{.underline}

[Hand-placed, formed concrete:]{.underline}

[Height of lining less than 1½ ft ....\...Vertical]{.underline}

[Hand-placed, screeded concrete:]{.underline}

[Height of lining less than 2½ ft \....3/4H to 1V\*]{.underline}\
[Height of lining more than 2½ ft .....1H to 1V]{.underline}

[Slip form concrete:]{.underline}

[Height of lining less than 3 ft \......\...1H to 1V]{.underline}\
[Height of lining more than 3 ft ....1¼H to 1V]{.underline}

[\*H -- Horizontal, V -- Vertical]{.underline}

**[Ditch or canal banks. ]{.underline}**[Ditch and canal banks shall be
constructed with earth to at least the top edge of the lining. In cut
sections, other than in rock, a berm shall be constructed not less than
2 in. above the top of the lining. Banks and berms shall be wide enough
to ensure stability of fills and to prevent excessive deposition in cut
sections.]{.underline}

[When using siphon tubes, minimum berm or bank width of 12 in. shall be
provided at the top of the lining on both sides of the finished ditch.
All other canals and laterals shall have a minimum berm or bank width of
18 in. at top of lining.]{.underline}

[If the bank or berm is to be used as a roadway, the minimum top width
shall be adequate for the purpose. Minimum recommended roadway width for
straight sections is 12 ft.]{.underline}

[Outside bank slopes and slopes above the berm elevation in cut sections
must be flat enough to insure stability. A minimum slope is 2H to 1V is
recommended. Where vegetation will be maintained by mowing, the minimum
slope shall be 3H to 1V.]{.underline}

**[Related structures]{.underline}**[. Plans for ditch or canal lining
installations shall provide for adequate inlets, outlets, turnouts,
checks, crossings, and other related structures needed for successful
conservation irrigation.]{.underline}

[Structures shall be constructed or installed in such a way that the
capacity or the freeboard of the ditch is not reduced and the
effectiveness of the lining is not impaired.]{.underline}

[All structures shall meet applicable NRCS Conservation Practice
Standard requirements for the type of structure used.]{.underline}

# [CONSIDERATIONS]{.underline}

[Effects of downstream flows or aquifers that would affect other water
usages or users.]{.underline}

[Potential changes in growth and transpiration of vegetation located
next to the conveyance because of elimination of leakage from the
system.]{.underline}

[Effects on the movement of dissolved substances into the
groundwater.]{.underline}

[Effects on wetlands or water-related wildlife habitats.]{.underline}

[Effects on the visual quality of water resources.]{.underline}

# [PLANS AND SPECIFICATIONS]{.underline}

Plans and specifications for installing plain concrete irrigation ditch
and canal linings shall be in keeping with this standard and shall
describe the requirements for applying the practice to achieve its
intended purpose.

# [OPERATION AND MAINTENANCE]{.underline}

[An operation and maintenance (O&M) plan shall be developed for plain
concrete irrigation ditch and canal linings. The plan should document
needed actions to ensure that practices perform adequately throughout
their expected life.]{.underline}

O&M requirements shall be determined as part of the design. Any
requirements should be documented as brief statements in the plans, the
specifications, or the conservation plan narrative, or as a separate O&M
plan. Typical O&M may include sediment/debris removal, patching of
cracked concrete, and replacement of deteriorated linings.