ASTM F449-02(2014)

Standard Practice for Subsurface Installation of Corrugated Polyethylene Pipe for Agricultural Drainage or Water Table Control

ABSTRACT
This practice covers the procedures for subsurface installation of corrugated polyethylene pipe, in accordance with the flexible conduit principles, intended for agricultural drainage or water table control. It is not however recommended for sanitary and storm sewer applications. General requirements for installation include: maximum and minimum burial depth; trench width; design of blinding, bedding, or envelope materials that are to be placed as the pipe is installed to ensure uniform continuous support; and granular or synthetic filters that are used to restrict the movement of particles into the pipe so as to maintain its hydraulic capacity. The pipe shall be aligned as smooth as possible with a curve radius larger than five times the pipe diameter while the backfill material shall be placed preferably on an angle to prevent pipe displacement or deflection. Stony trenches shall be avoided and any over-excavation or rock excavation shall be treated with proper bedding material. Factors that affect the proper handling of the pipe such as temperature; stretch caused by tension and bending forces; synthetic envelopes and filters that are subject to abrasion and tearing; and protection from fire hazards, livestock, heavy wheel traffic, and rodents or other animals shall also be considered during installation.
SCOPE
1.1 This practice is recommended for and limited to gravity flow subsurface drainage systems or water table control, but not recommended for sanitary or storm sewer applications. Procedures are outlined to minimize pipe deflection or structural damage during and after the installation process. These installation procedures are in accordance with “flexible conduit” principles.  
1.2 This practice applies to all agricultural subsurface drainage or water table control installations using Specification F405, F667 or other plastic pipe.  
1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 28-Feb-2014
• ICS: 23.040.20 - Plastics pipes
• Technical Committee: F17 - Plastic Piping Systems
• Drafting Committee: F17.65 - Land Drainage

Relations

• Replaces: ASTM F449-02(2008) - Standard Practice for Subsurface Installation of Corrugated Polyethylene Pipe for Agricultural Drainage or Water Table Control
• Effective Date: 01-Mar-2014
• Replaced By: ASTM F449-16 - Standard Practice for Subsurface Installation of Corrugated Polyethylene Pipe for Agricultural Drainage or Water Table Control
• Effective Date: 15-Feb-2016
• Referred By: ASTM F3219-19 - Standard Specification for 3 to 30 in. (75 To 750 mm) Polypropylene (PP) Corrugated Single Wall Pipe and Fittings
• Effective Date: 01-Mar-2014
• Referred By: ASTM F2648/F2648M-23 - Standard Specification for 50 mm to 1500 mm [2 in. to 60 in.] Annular Corrugated Profile Wall Polyethylene (PE) Pipe and Fittings for Land Drainage Applications
• Effective Date: 01-Mar-2014
• Referred By: ASTM F3390-20 - Standard Specification for 3 through 24 in. Lined Flexible Corrugated Polyethylene Pipe for Land Drainage Applications
• Effective Date: 01-Mar-2014
• Referred By: ASTM F2435-22 - Standard Specification for Steel Reinforced Polyethylene (PE) Corrugated Pipe
• Effective Date: 01-Mar-2014
• Referred By: ASTM F481-97(2019) - Standard Practice for Installation of Thermoplastic Pipe and Corrugated Pipe in Septic Tank Leach Fields
• Effective Date: 01-Mar-2014
• Referred By: ASTM F412-23 - Standard Terminology Relating to Plastic Piping Systems
• Effective Date: 01-Mar-2014
• Referred By: ASTM F667/F667M-16(2021) - Standard Specification for 3 through 24 in. Corrugated Polyethylene Pipe and Fittings
• Effective Date: 01-Mar-2014

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: F449 − 02(Reapproved 2014)
Standard Practice for
Subsurface Installation of Corrugated Polyethylene Pipe for
Agricultural Drainage or Water Table Control
ThisstandardisissuedunderthefixeddesignationF449;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
1.1 This practice is recommended for and limited to gravity
3.1 Definitions are in accordance with Terminology F412
flow subsurface drainage systems or water table control, but
and abbreviations are in accordance with Terminology D1600,
not recommended for sanitary or storm sewer applications.
unless otherwise specified.
Procedures are outlined to minimize pipe deflection or struc-
3.2 backfill—materials used to fill the trench following
tural damage during and after the installation process. These
installation of the pipe and bedding.
installation procedures are in accordance with “flexible con-
duit” principles.
3.3 bedding—material which provides stable bottom sup-
port for the pipe including the trench bottom groove support
1.2 This practice applies to all agricultural subsurface drain-
angle or select material placed around the pipe, and envelope
age or water table control installations using Specification
or filter materials where used during installation.
F405, F667 or other plastic pipe.
3.4 blinding—the placement of soil, bedding material over
1.3 The values stated in inch-pound units are to be regarded
and on the sides of the pipe or envelope to ensure proper grade,
as standard. The values given in parentheses are mathematical
alignment, support, and protection of pipe during backfilling
conversions to SI units that are provided for information only
and after installation.
and are not considered standard.
1.4 This standard does not purport to address all of the 3.5 boot (also shield)—the protecting apparatus linked to
safety concerns, if any, associated with its use. It is the the rear of the installation machine in a manner which allows
responsibility of the user of this standard to establish appro- placement of the pipe on the trench bottom, protection of the
priate safety and health practices and determine the applica- workman, or placement of envelope or filter material, or both.
bility of regulatory limitations prior to use.
3.6 cradle—a prefabricated rigid structure designed to pro-
vide trench bottom support for the pipe when soil support is
2. Referenced Documents
inadequate.
2.1 ASTM Standards:
3.7 envelope—porous material placed around the pipe to
D1600 Terminology forAbbreviatedTerms Relating to Plas-
provide bedding, improve the flow of ground water into the
tics
drain, or function as a filter.
D2412 Test Method for Determination of External Loading
Characteristics of Plastic Pipe by Parallel-Plate Loading
3.8 filter—an envelope of natural or synthetic materials
F405 Specification for Corrugated Polyethylene (PE) Pipe
placed completely around a drain to permit free water move-
and Fittings
ment into the drain, provide stabilizing support at the soil-filter
F412 Terminology Relating to Plastic Piping Systems
interface, and restrict movement of silt and sand into the drain.
F667 Specification for 3 through 24 in. Corrugated Polyeth-
3.9 grade—the slope of the pipe invert.
ylene Pipe and Fittings
3.10 groove support angle—angle between the radii of the
pipe at points of contact with the formed groove of undisturbed
This practice is under the jurisdiction of ASTM Committee F17 on Plastic
soil or a cradle.
Piping Systems and is the direct responsibility of Subcommittee F17.65 on Land
Drainage.
3.11 mineral soils—soil containing (1) less than 30 % or-
Current edition approved March 1, 2014. Published September 2014. Originally
ganicmatterbyweightprovidedthemineralfractionis60 %or
approvedin1976.Lastpreviouseditionapprovedin2008asF449 – 02(2008).DOI:
10.1520/F0449-02R14.
more clay, or (2) less than 20 % organic matter by weight
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
provided the mineral fraction has no clay, or (3) less than a
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
proportional content of organic matter between 20 and 30 % if
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. the clay content of the mineral fraction is between 0 and 60 %.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F449 − 02 (2014)
3.12 natural granular envelope—an envelope of granular
material, usually highly permeable well-graded sand and
gravel.
3.13 organic soil—soil containing (1) 30 % or more organic
matterprovidedthemineralfractionis60 %ormoreclay,or(2
) 20 % or more organic matter provided the mineral fraction
has no clay, or (3) a proportional content of organic matter
between 20 and 30 % if the clay content of mineral fraction is
between 0 and 60 %. (It is a general rule that a soil is classed
as an organic soil (histosol) either if more than one half of
upper 32 in. (80 mm) of soil is organic or if organic soil
material of any thickness rests on rock or on fragmental
material having voids filled with organic material.)
3.14 pipe stiffness—force per unit length, per unit deflection
as defined in Test Method D2412.
3.15 power feeder—mechanism that applies force to the
pipe as it passes through the boot or shield to reduce stretch
during installation.
3.16 pre-ripping—the practice of making a pass with the
plow without installing pipe to locate rocks and to reduce draft.
3.17 start hole—a trench sufficiently long and wide to allow
working room for placing the boot or shield, blade or cutting
mechanism on grade to start the trench and to install connec-
tions or pipe.
FIG. 1 Terminology for Installation of Plastic Drain Pipe
3.17.1 Discussion—Start holes are usually dug with a back-
hoe with a flat-bottom trench.
3.18 stretch—the increase in length of the pipe caused by
tension forces during installation. It is expressed as a percent
increase of the length prior to installation. Stretch differs from
elongation in that elongation is a material test and stretch is an
installation test.
3.19 synthetic envelope—an envelope made of synthetic
geotextiles, usually thin synthetic fabrics or thicker fibrous
material, or both, often selected to function as a filter.
3.20 trench depth—the depth of the trench measured from
the bottom of the pipe.
3.21 trench width—the width of the trench measured at the
top of the pipe.
3.22 Fig. 1 illustrates the terms bedding, vertical deflection,
backfill material, cover, groove support angle, horizontal
deflection, trench width, and trench depth.
FIG. 2 Support Grooves
Fig. 2 illustrates various support grooves or trench bottom
shapes.
Fig. 3 illustrates envelope and filter.
ft (0.6 m). Granular bedding or special construction techniques
Fig. 4 illustrates rodent protection devices.
may be used to reduce the cover. The time for consolidation of
Fig. 5 illustrates boot or shield.
backfill may be a factor (see 8.1). The minimum cover may
have limiting factors other than crushing such as clearance for
4. General Requirements
subsoiling and utility crossing
4.1 Burial—The maximum and minimum burial depth are 4.1.1.2 Organic Soils—Subsurface drains should be in-
affected by the following factors, groove support angle of the stalled in these soils only after initial subsidence has occurred.
trench bottom, bedding, blinding backfill soil density, envelope To produce initial subsidence open ditches should be con-
density, envelope placement, pipe stiffness, the live load structed in deep organic soils to carry off free water, and the
expected, desired water table depth, and width of trench. area should be allowed to stand or be partially cultivated for a
4.1.1 Minimum Depth: period of 3 to 5 years before installing pipe.The recommended
4.1.1.1 Mineral Soils—The minimum recommended cover minimum cover for the pipe in organic soils is 2.5 ft (0.7 m).
needed to protect the pipe from crushing under live loads is 2 If water level controls are not provided in the drainage system
F449 − 02 (2014)
4.3 Envelopes—Must be designed to provide adequate sup-
port for the pipe, improve the flow of ground water into the
pipe, and in some installations, filter flow into the pipe.
4.3.1 Natural Granular Envelopes—Minimum thickness of
75 mm (3 in.) around the pipe.
4.3.2 Synthetic Envelopes—Blinding or bedding is needed
to support and hold the envelope and pipe in place.
4.4 Filters—Are required when ground water can develop
velocities sufficient to move sand or silt, or both, into the drain.
Filters must be able to restrict the movement of these particles
into the pipe so that the hydraulic capacity of the pipe is
maintained.
4.4.1 Granular Filters—Design of a graded sand and fine
gravel filter should match the gradation of the specific soil
following criteria developed by the Natural Resource Conser-
vation Service, the U.S. Bureau of Reclamation, or the U.S.
Army Corps of Engineers.
4.4.2 Synthetic Filters—Thin synthetic fabric material or
geotextiles may be used where bedding, soil, and hydraulic
conditions permit. The openings in synthetic filters must be
compatible with the soil that surrounds the drain to prevent
excessive movement of soil that otherwise could plug the drain
or filter (see 5.3).
FIG. 3 Pipe Encased in Bedding for Support (left) and Pipe En-
NOTE 2—These filters must be specified to be compatible with the soil
cased in Sand and Gravel Envelope Designed as Filter (right)
type that encompasses the conduit since protective filters can plug and
decrease the inflow capability. Where fiberglass filter material is used, it
shall be manufactured from borosilicate-type glass and the manufacturer
shall certify that it is suitable for underground use.The fibers should be of
variable size, with some larger fibers intertwined in the mat in a random
to hold subsidence to a minimum, the depth of cover should be
manner.
increased to 3 ft (0.9 m).
NOTE 3—Vegetative filter material such as straw, hay, corn-cobs,
woodchips, sawdust, and coconut fiber are not recommended for use with
NOTE 1—These minimum depths are recommended to prevent crushing
flexible conduits because such conduits depend on the development of
of the pipe by normal agricultural vehicle loads. Other drainage factors
lateral support and these soft materials may not provide the necessary
such as those encountered with salinity control in arid irrigated lands may
lateral support.
require minimum depths of 6 ft (1.8 m).
4.5 Grade—Shall be as specified in the plan or guide.
4.1.2 Maximum Depth—The maximum burial depth is in-
Deviations greater than the following shall not be allowed.
fluenced by such factors as degree of compaction, type of
Vertical deviations of more than 0.1 ft (30.5 mm) in 10 ft (3.05
bedding, support from the trench bottom, trench width, size of
m). Negative grade that would fill the pipe more than 10 %.
pipe, pipe stiffness, weight of backfill, and live loads imposed.
Due to the speed of installation with the plow, automatic grade
Withoutanengineeringdesign,maximumburieddepthsshould
control is recommended. The pipe feeding system shall hold
be limited to those listed in Table 1. For installation at depths
thepipeinplaceinthebottomofthetrenchuntilsecuredbythe
greater than those listed in Table 1, specifications of and
bedding, blinding, or envelope material.
engineering design should be followed.
4.1.3 Trench Width—Increasing the trench width increases 4.6 Material Requirements—Pipe and fittings shall meet the
the soil load on the pipe. Side clearances of more than 150 mm requirements of the applicable ASTM standards referenced in
(6 in.) on each side should only be used with an engineering Section 2 and Table 1.
design and special construction (see Table 1). Trench width
5. Significant Factors in Pipe/Soil Interactions
must be at least 50 mm (2 in.) wider than the pipe on each side
for plow installation and 75 to 150 mm (3 to 6 in.) on each side 5.1 Connections—In start holes and adjacent open trenches,
for open trench installation to allow sufficient bedding to the pipe shall be aligned both vertically and horizontally,
support the pipe. If fine material cannot be placed alongside blinded and hand tamped along the sides of the pipe to prevent
and over the pipe, a wider trench should be considered or excessive deflection.
special bedding material supplied.
5.2 Deflection—The deflection of corrugated plastic pipe is
4.2 Design Items—It is particularly important that blinding, related to installation practice, bedding, groove support angle,
bedding, or envelope material be placed as the pipe is installed, blinding, gradation and density of soil, depth of installation,
to ensure uniform continuous support, so that the bedding, trench width in relation to pipe size, live loads imposed,
blinding, or envelope material can provide lateral restraint stretch, and pipe stiffness of pipe. Maximum pipe deflection
against pipe deflection as the backfill settles on the bedding, should be specified and not exceed 10 % of its nominal
blinding, or envelope material. diameter.
F449 − 02 (2014)
FIG. 4 Suggested Methods of Providing Rodent Protection for Outlet Pipes
5.3 Filters—Synthetic materials should never be used when 6.2 Backfilling—Place the backfill material so that displace-
the soil has a silt content greater than 40 %. ment or deflection of the pipe will not occur. This is preferably
on an angle, so the material flows down the front slope.Avoid
5.4 Trench Depth—See 4.1.
large stones, frozen material, and dry clods that cause concen-
5.5 Trench Width—The width of the trench or blade below
trated direct loads on the pipe. The trench should be backfilled
the top of the pipe should be adequate to allow placing pipe,
as soon as possible after blinding. When installing the pipe on
reducers,andconnectorsinthebottomofthetrenchandshould
a hot day back-filling should be delayed until pipe temperature
conform to 4.1.3.
cools to the soil temperature (see 8.1).
6. Construction
6.1 Alignment—Should be as smooth as possible with a
curve radius larger than five times the pipe diameter.
F449 − 02 (2014)
6.5 Bottom Shape—The bottom should be one of the shapes
shown in Fig. 2. The 90° “V” bottom of Fig. 2 works well on
nominalsizeslessthan200mm(8in.).Thepipeispressedinto
the void, which reduces horizontal deflection in the com
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: F449 − 02 (Reapproved 2008) F449 − 02 (Reapproved 2014)An American National Standard
Standard Practice for
Subsurface Installation of Corrugated Polyethylene Pipe for
Agricultural Drainage or Water Table Control
This standard is issued under the fixed designation F449; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice is recommended for and limited to gravity flow subsurface drainage systems or water table control, but not
recommended for sanitary or storm sewer applications. Procedures are outlined to minimize pipe deflection or structural damage
during and after the installation process. These installation procedures are in accordance with “flexible conduit” principles.
1.2 This practice applies to all agricultural subsurface drainage or water table control installations using Specification F405,
F667 or other plastic pipe.
1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D1600 Terminology for Abbreviated Terms Relating to Plastics
D2412 Test Method for Determination of External Loading Characteristics of Plastic Pipe by Parallel-Plate Loading
F405 Specification for Corrugated Polyethylene (PE) Pipe and Fittings
F412 Terminology Relating to Plastic Piping Systems
F667 Specification for 3 through 24 in. Corrugated Polyethylene Pipe and Fittings
3. Terminology
3.1 Definitions are in accordance with Terminology F412 and abbreviations are in accordance with Terminology D1600, unless
otherwise specified.
3.2 backfill—materials used to fill the trench following installation of the pipe and bedding.
3.3 bedding—material which provides stable bottom support for the pipe including the trench bottom groove support angle or
select material placed around the pipe, and envelope or filter materials where used during installation.
3.4 blinding—the placement of soil, bedding material over and on the sides of the pipe or envelope to ensure proper grade,
alignment, support, and protection of pipe during backfilling and after installation.
3.5 boot (also shield)—the protecting apparatus linked to the rear of the installation machine in a manner which allows
placement of the pipe on the trench bottom, protection of the workman, or placement of envelope or filter material, or both.
3.6 cradle—a prefabricated rigid structure designed to provide trench bottom support for the pipe when soil support is
inadequate.
3.7 envelope—porous material placed around the pipe to provide bedding, improve the flow of ground water into the drain, or
function as a filter.
This practice is under the jurisdiction of ASTM Committee F17 on Plastic Piping Systems and is the direct responsibility of Subcommittee F17.65 on Land Drainage.
Current edition approved Nov. 1, 2008March 1, 2014. Published November 2009September 2014. Originally approved in 1976. Last previous edition approved in
ε1
20022008 as F449 – 02 .(2008). DOI: 10.1520/F0449-02R08.10.1520/F0449-02R14.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F449 − 02 (2014)
3.8 filter—an envelope of natural or synthetic materials placed completely around a drain to permit free water movement into
the drain, provide stabilizing support at the soil-filter interface, and restrict movement of silt and sand into the drain.
3.9 grade—the slope of the pipe invert.
3.10 groove support angle—angle between the radii of the pipe at points of contact with the formed groove of undisturbed soil
or a cradle.
3.11 mineral soils—soil containing (1) less than 30 % organic matter by weight provided the mineral fraction is 60 % or more
clay, or (2) less than 20 % organic matter by weight provided the mineral fraction has no clay, or (3) less than a proportional content
of organic matter between 20 and 30 % if the clay content of the mineral fraction is between 0 and 60 %.
3.12 natural granular envelope—an envelope of granular material, usually highly permeable well-graded sand and gravel.
3.13 organic soil—soil containing (1) 30 % or more organic matter provided the mineral fraction is 60 % or more clay, or (2
) 20 % or more organic matter provided the mineral fraction has no clay, or (3) a proportional content of organic matter between
20 and 30 % if the clay content of mineral fraction is between 0 and 60 %. (It is a general rule that a soil is classed as an organic
soil (histosol) either if more than one half of upper 80 mm (32 in.)32 in. (80 mm) of soil is organic or if organic soil material of
any thickness rests on rock or on fragmental material having voids filled with organic material.)
3.14 pipe stiffness—force per unit length, per unit deflection as defined in Test Method D2412.
3.15 power feeder—mechanism that applies force to the pipe as it passes through the boot or shield to reduce stretch during
installation.
3.16 pre-ripping—the practice of making a pass with the plow without installing pipe to locate rocks and to reduce draft.
3.17 start hole—a trench sufficiently long and wide to allow working room for placing the boot or shield, blade or cutting
mechanism on grade to start the trench and to install connections or pipe.
3.17.1 Discussion—
Start holes are usually dug with a backhoe with a flat-bottom trench.
3.18 stretch—the increase in length of the pipe caused by tension forces during installation. It is expressed as a percent increase
of the length prior to installation. Stretch differs from elongation in that elongation is a material test and stretch is an installation
test.
3.19 synthetic envelope—an envelope made of synthetic geotextiles, usually thin synthetic fabrics or thicker fibrous material,
or both, often selected to function as a filter.
3.20 trench depth—the depth of the trench measured from the bottom of the pipe.
3.21 trench width—the width of the trench measured at the top of the pipe.
3.22 Fig. 1 illustrates the terms bedding, vertical deflection, backfill material, cover, groove support angle, horizontal deflection,
trench width, and trench depth.
Fig. 2 illustrates various support grooves or trench bottom shapes.
Fig. 3 illustrates envelope and filter.
Fig. 4 illustrates rodent protection devices.
Fig. 5 illustrates boot or shield.
4. General Requirements
4.1 Burial—The maximum and minimum burial depth are affected by the following factors, groove support angle of the trench
bottom, bedding, blinding backfill soil density, envelope density, envelope placement, pipe stiffness, the live load expected, desired
water table depth, and width of trench.
4.1.1 Minimum Depth:
4.1.1.1 Mineral Soils—The minimum recommended cover needed to protect the pipe from crushing under live loads is 0.6 m
(2 ft).2 ft (0.6 m). Granular bedding or special construction techniques may be used to reduce the cover. The time for consolidation
of backfill may be a factor (see 8.1). The minimum cover may have limiting factors other than crushing such as clearance for
subsoiling and utility crossing.
4.1.1.2 Organic Soils—Subsurface drains should be installed in these soils only after initial subsidence has occurred. To produce
initial subsidence open ditches should be constructed in deep organic soils to carry off free water, and the area should be allowed
to stand or be partially cultivated for a period of 3 to 5 years before installing pipe. The recommended minimum cover for the pipe
in organic soils is 0.7 m (2.5 ft).2.5 ft (0.7 m). If water level controls are not provided in the drainage system to hold subsidence
to a minimum, the depth of cover should be increased to 0.9 m (3 ft).3 ft (0.9 m).
NOTE 1—These minimum depths are recommended to prevent crushing of the pipe by normal agricultural vehicle loads. Other drainage factors such
as those encountered with salinity control in arid irrigated lands may require minimum depths of 1.8 m (6 ft).6 ft (1.8 m).
F449 − 02 (2014)
FIG. 1 Terminology for Installation of Plastic Drain Pipe
FIG. 2 Support Grooves
4.1.2 Maximum Depth—The maximum burial depth is influenced by such factors as degree of compaction, type of bedding,
support from the trench bottom, trench width, size of pipe, pipe stiffness, weight of backfill, and live loads imposed. Without an
engineering design, maximum buried depths should be limited to those listed in Table 1. For installation at depths greater than
those listed in Table 1, specifications of and engineering design should be followed.
4.1.3 Trench Width—Increasing the trench width increases the soil load on the pipe. Side clearances of more than 150 mm (6
in.) on each side should only be used with an engineering design and special construction (see Table 1). Trench width must be at
least 50 mm (2 in.) wider than the pipe on each side for plow installation and 75 to 150 mm (3 to 6 in.) on each side for open
trench installation to allow sufficient bedding to support the pipe. If fine material cannot be placed alongside and over the pipe,
a wider trench should be considered or special bedding material supplied.
4.2 Design Items—It is particularly important that blinding, bedding, or envelope material be placed as the pipe is installed, to
ensure uniform continuous support, so that the bedding, blinding, or envelope material can provide lateral restraint against pipe
deflection as the backfill settles on the bedding, blinding, or envelope material.
F449 − 02 (2014)
FIG. 3 Pipe Encased in Bedding for Support (left) and Pipe Encased in Sand and Gravel Envelope Designed as Filter (right)
4.3 Envelopes—Must be designed to provide adequate support for the pipe, improve the flow of ground water into the pipe, and
in some installations, filter flow into the pipe.
4.3.1 Natural Granular Envelopes—Minimum thickness of 75 mm (3 in.) around the pipe.
4.3.2 Synthetic Envelopes—Blinding or bedding is needed to support and hold the envelope and pipe in place.
4.4 Filters—Are required when ground water can develop velocities sufficient to move sand or silt, or both, into the drain. Filters
must be able to restrict the movement of these particles into the pipe so that the hydraulic capacity of the pipe is maintained.
4.4.1 Granular Filters—Design of a graded sand and fine gravel filter should match the gradation of the specific soil following
criteria developed by the Natural Resource Conservation Service, the U.S. Bureau of Reclamation, or the U.S. Army Corps of
Engineers.
4.4.2 Synthetic Filters—Thin synthetic fabric material or geotextiles may be used where bedding, soil, and hydraulic conditions
permit. The openings in synthetic filters must be compatible with the soil that surrounds the drain to prevent excessive movement
of soil that otherwise could plug the drain or filter (see 5.3).
NOTE 2—These filters must be specified to be compatible with the soil type that encompasses the conduit since protective filters can plug and decrease
the inflow capability. Where fiberglass filter material is used, it shall be manufactured from borosilicate-type glass and the manufacturer shall certify that
it is suitable for underground use. The fibers should be of variable size, with some larger fibers intertwined in the mat in a random manner.
NOTE 3—Vegetative filter material such as straw, hay, corn-cobs, woodchips, sawdust, and coconut fiber are not recommended for use with flexible
conduits because such conduits depend on the development of lateral support and these soft materials may not provide the necessary lateral support.
4.5 Grade—Shall be as specified in the plan or guide. Deviations greater than the following shall not be allowed. Vertical
deviations of more than 0.1 ft (30.5 mm) in 10 ft (3.05 m). Negative grade that would fill the pipe more than 10 %. Due to the
speed of installation with the plow, automatic grade control is recommended. The pipe feeding system shall hold the pipe in place
in the bottom of the trench until secured by the bedding, blinding, or envelope material.
4.6 Material Requirements—Pipe and fittings shall meet the requirements of the applicable ASTM standards referenced in
Section 2 and Table 1.
5. Significant Factors in Pipe/Soil Interactions
5.1 Connections—In start holes and adjacent open trenches, the pipe shall be aligned both vertically and horizontally, blinded
and hand tamped along the sides of the pipe to prevent excessive deflection.
5.2 Deflection—The deflection of corrugated plastic pipe is related to installation practice, bedding, groove support angle,
blinding, gradation and density of soil, depth of installation, trench width in relation to pipe size, live loads imposed, stretch, and
pipe stiffness of pipe. Maximum pipe deflection should be specified and not exceed 10 % of its nominal diameter.
5.3 Filters—Synthetic materials should never be used when the soil has a silt content greater than 40 %.
F449 − 02 (2014)
FIG. 4 Suggested Methods of Providing Rodent Protection for Outlet Pipes
5.4 Trench Depth—See 4.1.
5.5 Trench Width—The width of the trench or blade below the top of the pipe should be adequate to allow placing pipe, reducers,
and connectors in the bottom of the trench and should conform to 4.1.3.
6. Construction
6.1 Alignment—Should be as smooth as possible with a curve radius larger than five times the pipe diameter.
6.2 Backfilling—Place the backfill material so that displacement or deflection of the pipe will not occur. This is preferably on
an angle, so the material flows down the front slope. Avoid large sto
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