Natural Resources Conservation Service

Conservation Practice CONSTRUCTION Specification

Irrigation Water Conveyance

High-Pressure, Underground, Plastic Pipeline

Code 430DD

1.  SCOPE

> The work shall consist of installing underground thermoplastic
> pipelines ranging from ½ through 27 inches in diameter, closed to the
> atmosphere, and subject to internal pressures of 50 pounds per square
> inch or greater.

## SITE PREPARATION

Site preparation (mobilization and demobilization, clearing and
grubbing, structure removal, pollution control, and water for
construction) shall be in accordance with Construction Specification
587.

## MATERIALS

a.  **Quality of plastic pipe.** The compound used in manufacturing the
    pipe shall meet the requirements of one of the following materials:

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(1) **Polyvinyl chloride (PVC) as specified in ASTM D 1784.**

> \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

#### Material Code classification

> Type I, Grade 1 12454-B
>
> Type I, Grade 2 12454-C
>
> Type II, Grade 1 14333-D

(2) **Acrylonitrile-butadiene-styrene (ABS) as specified in ASTM D
    1788.**

> \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
>
> [Material Code classification]{.underline}
>
> Type I, Grade 2 5-2-2
>
> Type I, Grade 3 3-5-5
>
> Type II, Grade 1 4-4-5

(3) **Polyethylene (PE) as specified in ASTM D 1248.**

> \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

#### Material Code classification

> Grade P14, Class C IC-P14
>
> Grade P23, Class C IIC-P23
>
> Grade P33, Class C IIIC-P33
>
> Grade P34, Class C IVC-P34
>
> The pipe shall be homogeneous throughout and free from visible cracks,
> holes, foreign matter, or other defects. The pipe shall be as uniform
> in color, opacity, density, and other physical properties as is
> commercially practicable.

b.  **Markings**. Markings on the pipe shall include the following,
    which shall be spaced at intervals of not more than 5 ft:

-   Nominal pipe size.

-   Type of plastic pipe material, by designation code.

-   Pressure rating, psi, for water at 23 °C.

-   Manufacturer's name (or trademark) and code.

-   Specification designation with which the pipe complies:

    1.  IPS-size pipe, the ASTM specification. Pipe meeting one of the
        ASTM specifications listed for IPS-size pipe and intended for
        the transport of potable water shall also be marked with the
        seal of a recognized laboratory making the evaluation for this
        purpose.

    2.  For plastic irrigation pipe, the designation PIP.

c.  **Pipe requirements**. All pipe installed under this standard shall
    be pressure rated for water.

> The relationship between standard dimension ratios, dimensions,
> hydrostatic design stresses, and pressure ratings shall be determined
> by one of the following formulas:
>
> For PVC, ABS, and PE pipe with outside diameter controlled: 2S/P =
> D~o~/t - 1 or 2S/P = R -- 1
>
> For PE pipe with inside diameter controlled: 2S/P = D~i~ /t + 1 or
> 2S/P = R + 1
>
> Where:
>
> S = hydrostatic design stress, psi.
>
> P = pressure rating, psi.
>
> D~o~ = average outside diameter in inches.
>
> D~I~ = average inside diameter in inches.
>
> t = minimum wall thickness in inches.
>
> R = standard dimension ratio (SDR).
>
> Hydrostatic design stresses for the plastic pipe material are given in
> **Table 1**.

**[Table 1]{.underline}**

Hydrostatic design stress and designation Plastic Pipe

+-------------------------+--------------------+-----------------------+
| Material                | Hydraulic Design   | **Designation on      |
|                         | Stress (psi.)      | Pipe**                |
+-------------------------+--------------------+-----------------------+
| PVC Type I, Grade 1     | > 2,000            | **PVC 1120**          |
+-------------------------+--------------------+-----------------------+
| PVC Type I, Grade 2     | > 2,000            | **PVC 1220**          |
+-------------------------+--------------------+-----------------------+
| PVC Type II, Grade 1    | > 1,000            | **PVC 2110**          |
+-------------------------+--------------------+-----------------------+
| PVC Type II, Grade 1    | > 1,250            | **PVC 2112**          |
+-------------------------+--------------------+-----------------------+
| PVC Type II, Grade 1    | > 1,600            | **PVC 2116**          |
+-------------------------+--------------------+-----------------------+
| ABS Type I, Grade 2     | > 800              | **ABS 1208**          |
+-------------------------+--------------------+-----------------------+
| ABS Type I, Grade 2     | > 1,000            | **ABS 1210**          |
+-------------------------+--------------------+-----------------------+
| ABS Type I, Grade 3     | > 1,600            | **ABS 1316**          |
+-------------------------+--------------------+-----------------------+
| ABS Type II, Grade 1    | > 1,250            | **ABS 2112**          |
+-------------------------+--------------------+-----------------------+
| PE Grade P14            | > 400              | **PE 1404**           |
+-------------------------+--------------------+-----------------------+
| PE Grade P23            | > 500              | **PE 2305**           |
+-------------------------+--------------------+-----------------------+
| PE Grade P23            | > 630              | **PE 2306**           |
+-------------------------+--------------------+-----------------------+
| PE Grade P33            | > 630              | **PE 3306**           |
+-------------------------+--------------------+-----------------------+
| PE Grade P34            | > 630              | **PE 3406**           |
+-------------------------+--------------------+-----------------------+
| **PE Grade P34**        | > **800**          | **PE 3408**           |
+-------------------------+--------------------+-----------------------+

> Iron pipe size (IPS) (outside diameter same as that for iron pipe
> sizes) and I.D. controlled PE pipe manufactured, tested, and marked to
> meet one of the following ASTM specifications shall be acceptable
> under this standard.
>
> [ASTM Specification for:]{.underline}
>
> D 1785 - Polyvinyl chloride (PVC) Plastic Pipe, Schedules 40, 80 and
> 120;
>
> D 2241 - Polyvinyl chloride (PVC) Plastic Pipe, (SDR-PR);
>
> D 2672 - Bell-End Polyvinyl chloride (PVC) Plastic Pipe;
>
> D 2740 - Polyvinyl chloride (PVC) Plastic Tubing;
>
> D 1527 - Acrylonitrile-Butadiene-Styrene (ABS) Plastic Pipe, Schedules
> 40 and 80;
>
> D 2282 - Acrylonitrile-Butadiene-Styrene (ABS) Plastic Pipe (SDR-PR);
>
> D 2104 - Polyethylene (PE) Plastic Pipe, Schedule 40;
>
> D 2239 - Polyethylene (PE) Plastic Pipe, (SDR-PR);
>
> D 2447 - Polyethylene (PE) Plastic Pipe, Schedules 40 and 80, based on
> outside diameter;
>
> D 2737 - Polyethylene (PE) Plastic Tubing;
>
> D 3035 - Polyethylene (PE) Plastic Pipe, (SDR-PR), Based on controlled
> outside diameter;
>
> F 771 - Polyethylene (PE) Thermoplastic High-Pressure Irrigation
> Pipeline Systems;
>
> Plastic irrigation pipe (PIP) shall meet the requirements of ASTM
> Specification D 2241 or of ASTM D 2282 except that:

-   The sustained pressure test shall not be required.

-   The burst pressure tests shall be performed according to the
    procedures listed in ASTM Specification D 2241 or D 2282 and shall
    meet the applicable requirements given in these ASTM's or those
    listed below for the standard dimension ratios (SDR's) currently not
    included in ASTM Specification D 2241 or D 2282.

> The [minimum]{.underline} burst pressure requirements for water at
> 23°C (73.4°F) for [PVC 1120 and PVC 1220]{.underline} plastic pipe for
> SDR 51 is 260 psi. The design stress levels used for the test
> pressures are: PVC 1120 and 1220 -- 6,400 psi.
>
> Burst pressure requirements for water at 23°C (73.4°F) for
> [ABS]{.underline}^1^ plastic pipe are:

+----------------------------+--------------------+-------------------+
| SDR                        | > **Minimum burst  |                   |
|                            | > pressure**       |                   |
+----------------------------+--------------------+-------------------+
|                            | > ABS 2112         | > **ABS 1316**    |
+----------------------------+--------------------+-------------------+
| 32.5                       | > 420 psi.         | **380 psi**       |
+----------------------------+--------------------+-------------------+
| **41**                     | **-**              | **300 psi**       |
+----------------------------+--------------------+-------------------+

> ^1^The fiber stresses used to drive these test pressures are: ABS
> 2112-6,600 psi; ABS 1316-6,000 lb/in^2^. To simplify testing, minor
> adjustments have been made to keep the test pressures uniform.

**Table 2**

Pressure rating factors for PVC and PE pipe for water at elevated
temperatures

  ------------------------- --------------------- -----------------------
  Temperature °F            PVC Factor            **PE Factor**

  73.4                      1.00                  **1.00**

  80                        0.88                  **0.93**

  90                        0.75                  **0.81**

  100                       0.62                  **0.70**

  110                       0.50                  **-**

  120                       0.40                  **-**

  130                       0.30                  **-**

  **140**                   **0.22**              **-**
  ------------------------- --------------------- -----------------------

> To obtain the pipe's reduced pressure rating because of water
> temperatures above 73.4 °F, multiply normal pressure rating by the
> appropriate factor from table.

d.  **Fittings and couplers**. All fittings and couplers shall meet or
    exceed the same strength requirements as those of the pipe and shall
    be made of material that is recommended for use with the pipe.

> The ASTM specifications for fittings suitable for use with IPS-size
> pipe and inside diameter controlled PE pipe covered by this standard
> are:
>
> [ASTM Specification for:]{.underline}
>
> D 2466 - Socket-type Polyvinyl chloride (PVC) Plastic Pipe, Schedule
> 40;
>
> D 2467 - Socket-type Polyvinyl chloride (PVC) Plastic Pipe, Schedule
> 80;
>
> D 2468 - Socket-type Acrylonitrile-Butadiene-Styrene (ABS) Plastic
> Fittings, Schedule 40;
>
> D 2609 - Plastic Insert Fittings for Polyethylene (PE) Plastic Pipe;
>
> D 2683 - Socket-type Polyethylene Fittings for SDR 11.0 Polyethylene
> Pipe;
>
> D 3139 - Standard Specification for Plastic Pressure Pipe using
> Flexible Elastomeric Seals;
>
> D 3261 - Butt Heat Fusion Polyethylene (PE) Plastic Fittings for
> Polyethylene (PE) Plastic Pipe and Tubing.
>
> Plastic pipe (PIP) shall have belled ends or separate couplers and
> fittings that are suitable for joining the pipe and appurtenances by
> solvent cement, rubber gaskets, or other methods recommended by the
> pipe manufacturer. Such fittings and joints shall be capable of
> withstanding a working pressure equal to or greater than that for the
> pipe.

e.  **Solvent cement joints**. Solvent for solvent cement joints shall
    conform to ASTM Specification D 2564 for PVC pipe and fittings and
    to D 2235 for ABS pipe and fittings.

> Solvent cement joints shall be used and constructed according to the
> recommendations of the pipe manufacturer.

f.  **Rubber gasket joints**. Rubber gasket joints shall conform to ASTM
    Specification D 3139.

g.  **Wall thickness.** The wall thickness for all pipe installed under
    this standard, regardless of pressure rating or type, shall not be
    less than 0.060 inches.

h.  **Exposed PVC.** PVC exposed to the sun, will oxidize from
    ultraviolet (UV) radiation. The material will also become brittle.
    If stored outside for more than 15 days, cover PVC with a
    light-colored, durable, opaque material, vented to prevent heat
    buildup. Paint any exposed PVC pipe installation with a heavily
    pigmented latex or acrylic paint, chemically compatible with PVC.
    While color is not particularly important for UV protection, use
    light paint colors to reduce pipe temperature.

## INSTALLATION

a.  **Minimum depth of cover.** Pipe shall be installed at sufficient
    depth below the ground surface to provide protection from hazards
    imposed by traffic crossings, farming operations, freezing
    temperatures, or soil cracking. The minimum depth of cover for pipe
    susceptible to any of these hazards shall be:

  ----------------------------------- -----------------------------------
  Pipe Diameter (in.)                 **Depth of cover (in.)**

  ½ through 2 ½                       **18**

  3 through 5                         **24**

  **6 or more**                       **30**
  ----------------------------------- -----------------------------------

> In areas where the pipe will not be susceptible to freezing and
> vehicular or cultivation hazards and the soils do not crack
> appreciably when dry, the minimum depth of cover may be reduced to:

  ----------------------------------- -----------------------------------
  Pipe Diameter (in.)                 **Depth of cover (in.)**

  ½ through 1 ½                       **6**

  2 through 3                         **12**

  4 through 6                         **18**

  **More than 6**                     **24**
  ----------------------------------- -----------------------------------

> The minimum cover for polyethylene pipe is 6 in but may be reduced to
> 2 in where conditions warrant. Rubber gasket joints may be used
> following normal bedding procedures where coarse sand or cement layers
> exist.
>
> At low places on the ground surface, extra fill may be placed over the
> pipeline to provide the minimum depth of cover. The top width of the
> fill shall then be no less than 10 ft and the side slopes no steeper
> than 6:1. If extra protection is needed at vehicle crossings,
> encasement pipe or other approved methods may be used.

b.  **Trench construction**. The trench at any point below the top of
    the pipe shall be only wide enough to permit the pipe to be easily
    placed and joined and to allow the initial backfill material to be
    uniformly placed under the haunches and along the side of the pipe.
    The maximum trench width shall be 36 in greater than the diameter of
    the pipe. If the trench is precision excavated and has a
    semicircular bottom that closely fits the pipe, the width shall not
    exceed the outside diameter of the pipe by more than 10 percent.

> The trench bottom shall be uniform so that the pipe lies on the bottom
> without bridging. Clods, rocks, and uneven spots that can damage the
> pipe or cause non-uniform support shall be removed.
>
> If rocks, boulders, or any other material that can damage the pipe are
> encountered, the trench bottom shall be undercut a minimum of 4 in
> below final grade and filled with bedding material consisting of sand
> or compacted fine-grained soils.
>
> Pipelines having a diameter of ½ through 2 ½ in that are to be placed
> in areas not subject to vehicular loads and in soils that do not crack
> appreciably when dry may be placed by using "plow-in" equipment
> instead of conventional trenching.
>
> Provisions shall be made to insure safe working conditions where
> unstable soil, trench depth, or other conditions can be hazardous to
> personnel working in the trench.

c.  **Placement.** Care shall be taken to prevent permanent distortion
    and damage when handling the pipe during unusually warm or cold
    weather. The pipe shall be allowed to come within a few degrees of
    the temperature it will have after it is completely covered before
    placing the backfill, other than that needed for shading, or before
    connecting the pipe to other facilities. The pipe shall be uniformly
    and continuously supported over its entire length on firm stable
    material. Blocking or mounding shall not be used to bring the pipe
    to final grade.

> For pipe with bell joints, bell holes shall be excavated in the
> bedding material, as needed, to allow for unobstructed assembly of the
> joint and to permit the body of the pipe to be in contact with the
> bedding material throughout its length.

d.  **Joints and connections.** All joints and connections shall be
    designed and constructed to withstand the design maximum working
    pressure for the pipeline without leakage and to leave the inside of
    the line free of any obstruction that may tend to reduce its
    capacity below design requirements.

> All fittings, such as couplings, reducers, bends, tees, and crosses,
> shall be installed according to the recommendations of the pipe
> manufacturer.
>
> Fittings made of steel or other metals susceptible to corrosion shall
> be adequately protected by being wrapped with plastic tape or by being
> coated with a substance that has high corrosion-preventative
> qualities. If plastic tape is used, all surfaces shall be thoroughly
> cleaned and coated with a primer compatible with the tape before
> wrapping.

e.  **Thrust blocks.** Thrust blocks must be formed against a solid
    hand-excavated trench wall undamaged by mechanical equipment. They
    shall be constructed of concrete, and the space between the pipe and
    trench wall shall be filled to the height of the outside diameter of
    the pipe or as specified by the manufacturer.

f.  **Testing.** The pipeline shall be tested for pressure strength,
    leakage, and proper functioning. The tests may be performed before
    backfilling or anytime after the pipeline is ready for service.

> Tests for pressure strength and leaks shall be accomplished by
> inspecting the pipeline and appurtenances while the maximum working
> pressure is maintained and all joints and connections are uncovered,
> or by observing normal operation of the pipeline after it is put into
> service. Partial backfills needed to hold the pipe in place during
> testing shall be placed as specified in "Initial Backfill." Any leaks
> shall be repaired and the system retested.
>
> The pipeline shall be tested to insure that it functions properly at
> design capacity. At or below design capacity there shall be no
> objectionable flow conditions. Objectionable flow conditions shall
> include water hammer, continuing unsteady delivery of water, damage to
> the pipeline, or detrimental discharge from control valves.

g.  **Initial backfill.** Hand, mechanical, or water packing methods may
    be used.

> The initial backfill material shall be soil or sand that is free from
> rocks or stones larger than 1 in. in diameter. At the time of
> placement, the moisture content of the material shall be such that the
> required degree of compaction can be obtained with the backfill method
> to be used. The initial backfill material shall be placed so that the
> pipe will not be displaced, excessively deformed, or damaged.
>
> If backfilling is done by hand or mechanical means, the initial fill
> shall be compacted firmly around and above the pipe as required to
> provide adequate lateral support to the pipe. If the water packing
> method is used, the pipeline first shall be filled with water. The
> initial backfill before wetting shall be of sufficient depth to insure
> complete coverage of the pipe after consolidation. Water packing is
> accomplished by adding enough water to diked reaches of the trench to
> thoroughly saturate the initial backfill without excessive pooling.
> After the backfill is saturated, the pipeline shall remain full until
> after the final backfill is made. The wetted fill shall be allowed to
> dry until firm before beginning the final backfill.

h.  **Final backfill.** The final backfill material shall be free of
    large rocks, frozen clods, and other debris greater than 3 in. in
    diameter. The material shall be placed and spread in approximately
    uniform layers so that there will be no unfilled spaces in the
    backfill and the backfill will be level with the natural ground or
    at the design grade required to provide the minimum depth of cover
    after settlement. Rolling equipment shall not be used to consolidate
    the final backfill until the specified minimum depth of cover has
    been placed.

> All special backfilling requirements of the pipe manufacturer shall be
> met.

i.  **Basis of acceptance.** The acceptability of the pipeline shall be
    determined by inspections to check compliance with all the
    provisions of this standard with respect to the design of the line,
    the pipe and pipe marking, the appurtenances, and the minimum
    installation requirements.

j.  **Certifications and guarantee.** If requested by the state
    conservation engineer, a qualified testing laboratory must certify
    with supporting test results that the pipe meets the requirements
    specified in this standard. The seal of approval of a recognized
    laboratory on pipe bearing one of the ASTM specifications listed in
    this standard may be accepted for this certification.

> The installing contractor shall certify that his or her installation
> complies with the requirements of this standard. He or she shall
> furnish a written guarantee that protects the owner against defective
> workmanship and materials for not less than 1 year. The certification
> identifies the manufacturer and markings of the pipe used.

5.  **MEASUREMENT**

> The quantity of each size, type, and class of pipe shall be determined
> to the nearest foot by measurement of the laid length of pipe along
> the crown centerline of the conduit.
>
> Project Name:
>
> Date:

6.  **ITEMS OF WORK AND CONSTRUCTION DETAILS**

> Items of work to be prepared in conformance with this specification
> and the construction details are: