Group Title: Ft. Pierce AREC
Title: Design considerations for plastic drain tiles in Florida citrus groves
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Permanent Link: http://ufdc.ufl.edu/UF00055960/00001
 Material Information
Title: Design considerations for plastic drain tiles in Florida citrus groves
Series Title: Ft. Pierce AREC
Physical Description: 4 leaves : ; 28 cm.
Language: English
Creator: Boman, Brian J
Agricultural Research and Education Center (Fort Pierce, Fla.)
Publisher: University of Florida, Insititute of Food and Agricultural Sciences, Agricultural Research and Education Center
Place of Publication: Fort Pierce Fla
Publication Date: 1993]
 Subjects
Subject: Citrus -- Irrigation -- Florida   ( lcsh )
Drainage -- Florida   ( lcsh )
Drain-tiles -- Florida   ( lcsh )
Genre: non-fiction   ( marcgt )
 Notes
Statement of Responsibility: Brian J. Boman.
General Note: Caption title.
 Record Information
Bibliographic ID: UF00055960
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 66899372

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HISTORIC NOTE


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida









* 3 -( DESIGN CONSIDERATIONS FOR PLASTIC A 7 o 20 j

DRAIN TILES IN FLORIDA CITRUS GROVES ,... .
o' orf Flori'a

BRIAN J. BOMAN
Agricultural Research and Education Center
P.O. Box 248, Ft. Pierce, FL 34954


CORRUGATED PLASTIC POLYETHYLENE TUBING
Corrugated plastic drain tubing should meet the
requirements of ASTM Standards F405 and F667 which among
other aspects define quality classes. Standard tubing is
satisfactory for most agricultural applications. Heavy duty
tubing is recommended where wide trenches are required,
where side support is poor, in very narrow trenches (< 3
pipe diameters), and where rocky soil conditions are
expected.
Tubing normally used in agricultural operations is 4
inches or greater in diameter. The tubing is available in
coils of various lengths, depending upon the diameter of the
tubing. Water enters the plastic tubing through small
openings located in the valleys between corrugations. The
flexible drain tubing gains most of its load bearing
*capacity by support from soil at the sides of the tubing.
A load on top of the tubing causes the sidewalls to bulge
outward against the soil. The soil resists the bulging, and
the effect is to give the tubing a greater load-bearing
capacity. The tubing must have sufficient strength to
withstand the soil load without excessive deflection,
collapse on top, or failure of the sidewalls.
Corrugated plastic drain tubing has several desirable
characteristics. The tubing is light and flexible, weighing
about 85 lbs per 250 ft of 4 inch tubing. The tubing allows
good alignment in unstable soils. Long lengths with no open
joints make good installation relatively easy.

DESIGN CONSIDERATIONS
The initial consideration of suitability of tile drains
on a particular area requires a topographic survey. Since
most of the Flatwoods citrus areas are either nearly level
or of basin-type topography, sufficient slope for gravity
outfall probably won't exist. Therefore, a drainage pump
for the outlet will most likely be needed. Aerial
photographs along with the survey should facilitate
selecting a suitable site for the drainage sump in a low
area of the grove.
A survey will also help determine if leveling of the
land is required. Open ditches and water furrows may be
required to remove bulk of surface water. If shallow beds
0 are to be constructed, they should be designed to minimize


Ft. Pierce AREC 93-6





q


the quantity of earth moved leveling process. Drains should
be installed in direction of greatest slope.
There are several important soil factors that should be
obtained from a soil survey of the area prior to the drain
design. These factors include:
1. Soil types
2. Thickness of various strata
3. Continuity of strata
4. Position of strata with respect to ground surface
5. Hydraulic conductivity and porosity of various
strata
a. The hydraulic conductivity is the rate at
which water moves through soil in units of
distance/time (in/hr or ft/day). It varies
tremendously with soil moisture content and
is usually specified under saturated
conditions.
b. Porosity is the volume of pores (air space)
divided by the total volume of soil. It
determines how much water can drain out of
the soil as the water table is lowered.
Several water factors need to be considered to ensure
a proper design of the drainage system. Historical records
can be examined to determine the relationship between
rainfall and water table fluctuations. The source of all
water coming into an area must be determined. If the water
table is built up by irrigation, it may indicate that there
is an improper system design and that better management or
a change in design may alleviate some of the water table
problems. Seepage from reservoirs and ditches is often a
source of high water tables in nearby areas of the grove.
Money spent on perimeter ditches or throw-out pumps may
decrease the drainage requirement. If there are free-
flowing artesian wells, they should be capped or plugged.

Drain Depth
The drain depth is often controlled by the depth of the
outlet. Drains should be placed in the most permeable
layer possible. However, the drain must be installed
on the specified grade throughout length, even if it
means installation in a less permeable horizon.

Alignment
Changes in the horizontal direction should be minimized -
and made in such a way that the specified grade is
maintained. The change of alignment should be made
with a gradual curve, the use of manufactured bends or
fittings, or the use of junction boxes or manholes.

Drain capacity
The drainage coefficient should be at least 0.5 to 0.75
inches per day for most groves. This will allow water
table drawdowm or 4-6 inches per day, which should be


Ft. Pierce AREC 93-6









adequate to prevent root damage. If surface water must
also be removed, the drainage coefficient should be
doubled to accommodate the extra water which needs to
pass through the drains.

Spacing
The dpacing between drains depends on depth installed,
the hydraulic conductivity, and the amount of water to
be drained. When two (or more) drain lines are
installed, each one exerts an influence on the water
table and the drawdown curves intersect at the midpoint
between the drains. As the drains are moved closer
together, the curves intersect at a lower level at the
midpoint between drains. General drain spacing
distances by soil types are presented in University of
Florida, IFAS, Extension Circular 661, A Guide for
Plastic Tile Drainage in Florida Citrus Groves by H. W.
Ford, B. C. Belville, and V. C. Carlisle. Site
specific drain spacings can be calculated by several
methods using measured field data (see Drainage for
Agriculture, Agronomy Monograph No. 17, J. Van
Schilfgaarde, Ed. American So. Agronomy, Madison, WI,
1974).

Grade
The grade at which the drain is installed should be
based on site conditions, size of drain, and quality of
installation. Minimums are:
4-inch = 0.10% 1.2 inches per 100 ft
5-inch = 0.07% 0.8 inches per 100 ft
6-inch = 0.05% 0.6 inches per 100 ft
The maximum slope should result in a flow velocity not
exceeding 3.5 fps for sand and sandy loam soils and 7.0
fps for clay soils. Velocities exceeding these rates
require protective measures such as air vents or relief
wells. A gradual variation of up to 0.1 ft from the
specified grade is allowable in most cases.

Connections
Manufactured couplers or fittings should be used at all
joints. All connections must be compatible with the
pipe. All fittings should be securely joined so they
cannot come apart in the installation process, and the
envelop material or "sock" should be also be taped or
secured to provide integrity to the entire drain after
installation.

Outlet
Sumps should be located at low end of collector ditch.
A float-controlled pump resulting in automatic
operation is preferred. The pump should be sized to
remove the design capacity for the drained area. Drain
tubing outlets should be 6 inches above the normal


Ft. Pierce AREC 93-6





4* 1 1. W4


water level in the ditch (may be submerged during
storms). In addition to sunlight weakening the plastic
drainage tubing, tubing can be destroyed by fire or
damaged by rodents or ditch maintenance procedures.
Therefore, the discharge end should be rigid PVC. At
least 2/3 of its length should be embedded in the ditch
bank. The rigid outlet pipe may need an animal guard of
swinging gates, rods, screens to keep rodents from
entering and plugging the tubing.


INSTALLATION CONSIDERATIONS
Tubing should be installed so that it does not deflect
more than 20% of its nominal diameter. The plastic tubing
has reduced strength at high temperatures. During
installation on hot sunny days, the temperature of the
tubing can reach over 1200F. The strength of 4-inch tubing
is reduced 50% when temperature is raised from 700F to 1200F.
Therefore, precautions must be taken to prevent sharp
impacts, heavy objects, or excessive pull on tubing during
installation.
The strength of the tubing can also be reduced by
stretching occurring during installation. The amount of
stretch during installation is influenced by the
temperature, the amount and duration of drag encountered
when the tubing is fed through the installation machine, and
the stretch-resistance of the tubing. Stretch should not
exceed 5%. A 5% stretch reduces strength by about 11%.
Plastic tubing will float in water. During
installation, it is essential that backfill material is
placed around the tubing immediately and correctly if water
is present so that the tubing does not get misaligned.
Care should be taken in all soils to prevent surface
soil that contains organic material from being placed around
the drain tubing. Likewise, the tubing should not be bedded
in the organic layer of spodic soils. The organic material
tends to trap iron and provide an energy source for the iron
reducing bacterial which cause ochre buildup.
Upon completion of installation, a map or aerial
photograph with the drains located should be prepared
immediately to identify the precise location of the drain
lines. Drain lines can be located using a small rod (3/8
inch) with a sharpened tip to probe for the tubing. The
probe may penetrate the tubing when it is found, but it will
not seriously damage it as the hole will tend to close when
the probe is withdrawn.


Ft. Pierce AREC 93-6




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