NATURAL RESOURCES CONSERVATION SERVICE

**Idaho**

**CONSTRUCTION SPECIFICATIONS**

**FOR**

> **IRRIGATION WATER CONVEYANCE**
>
> **CORRUGATED METAL PIPELINE**

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

(Owner/Operator)

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

(Project/Title)

GENERAL

Pipelines shall be installed in accordance with a design and plan
approved by the responsible technician. Details of construction shown in
the design and plan but not included here shall be considered as a part
of this specification. Construction activities shall be in accordance
with applicable OSHA regulations.

PIPE INSTALLATION

Pipe shall be the diameter, length, gage or thickness, material type and
coated as specified on the drawings.

The pipe shall be handled in a manner so as to prevent damage to the
pipe and abrasion to the coating. Individual joints of pipe shall be
inspected and any damaged pipe shall be removed and replaced. The pipe
shall not be dragged or rolled on the ground.

Pipe shall be laid to the lines and grades as shown on the drawings.

UNDERGROUND PIPELINES

[Trench]{.underline}. Trench width at any point below the top of the
pipe should 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 sides of the pipe. The maximum trench
width shall be 30 inches greater than the diameter of the pipe. The
minimum trench width shall be not less than the pipe diameter plus 18
inches, unless the trench is precision excavated with a semicircular
bottom that closely fits the pipe and the width does not exceed the
outside diameter of the pipe by more than 10 percent.

Trench banks that are more than 5 feet high shall be shored or sloped.

Where rock, hardpan, cobbles or other hard material which might prevent
the pipe from being uniformly supported is encountered in the bottom of
the trench, the trench shall be undercut a minimum of four inches below
final grade. The over cut area of the trench will then be filled with
sand or fine-grained soil.

[Bedding]{.underline}. The pipe shall be firmly and uniformly bedded
throughout its entire length. Bedding material shall be placed and
spread in uniform layers and in such a manner as to fill the trench so
there are no unfilled spaces below the pipe. For pipe with bell joints,
holes shall be dug in the bedding at the bells to permit the body of the
pipe to be in contact with the bedding along its entire length. Blocking
or mounding shall not be used to bring the pipe up to final grade.

Hand, mechanical or water packing are optional methods for placing and
compacting pipe backfill.

[Initial Backfill]{.underline}. The initial backfill material shall be
either (1) angular 1 to ¼ inch size crush stone with a maximum of 10
percent cohesive fines or (2) sand and gravels (Soil types GW, GP, SW,
and SP) with a maximum particle size of 1 inch containing a maximum of
12 percent of noncohesive fines. Sands shall have a maximum of 45
percent passing the \# 40 sieve. The on site trench excavated materials
may be used if they meet the above requirements. The initial backfill
materials shall be placed in a manner as not to displace, deform or
damage the pipe.

When backfilling is done by hand or mechanical means the initial fill
shall be compacted firmly around and under the pipe to achieve a soil
density equal or greater than the density of the undisturbed side walls
of the trench. The thickness of individual lifts prior to compaction
shall not exceed 6 inches.

When water packing is used, the pipe shall be filled with water. The
initial backfill, before wetting, shall be of sufficient depth to ensure
complete coverage of the pipe with backfill after consolidation has
taken place. Water packing shall be accomplished by adding water to
diked reaches of the trench in such quantity as to thoroughly saturate
the initial backfill. After the backfill is saturated, the fill shall be
consolidated by rodding or with a vibrator. The wetted fill shall be
allowed to dry until firm before completing the final backfill. The
pipeline shall remain full of water until after the final backfill is
made.

[Final Backfill]{.underline}. The final backfill material shall be free
of rocks, frozen clods or other debris larger than 1 inch in diameter
within 6 inches of the pipe and 6 inches in particle size for the
remaining portion of the final backfill unless otherwise specified on
the drawings. The material shall be placed and spread in approximately
uniform layers so there are no unfilled spaces in the backfill. Final
backfill may be mounded over the top of the trench above ground level,
but in no case shall the final backfill be lower than the natural ground
along the top of the trench.

All special backfilling requirements of the pipe manufacturer shall be
followed.

[Cover]{.underline}. Unless a greater depth is shown on the drawings,
the minimum depth for backfill over the top of the pipe is 12 inches.

At low places on the ground surface or at locations where it is shallow
to rock, extra fill may be placed over the pipeline to provide the
minimum depth of cover. In such cases, the top width of the fill shall
be no less than 10 feet and the side slopes no steeper than 6 horizontal
to 1 vertical.

Vertical alignment of pipe shall be uniform and such as to maintain the
cover requirements unless otherwise noted on the drawings.

[Thrust Blocks]{.underline}. Thrust blocks shall be formed against a
solid trench wall. They shall be of the minimum size and materials as
specified on the drawings.

ABOVE GROUND PIPELINES

Concrete, timber or other specified pipe supports and anchor and thrust
blocks shall be constructed at the locations and to the dimensions shown
on the drawings. The pipe shall be a minimum of 8 inches off of the
ground along the entire length of the pipeline. Supports shall be set on
a firm, stable base. Timber supports shall be treated with a wood
preservative meeting the requirements of ASTM D 1760.

ON-GROUND PIPELINES

The ground shall be shaped to provide continuous support along the
bottom 1/4 to 1/3 of the pipe circumference. Where rock, hardpan or
other materials which might damage the pipe are encountered, the ground
surface will be lowered a minimum of 4 inches and the backfilled with
sand or fine-grained soil.

Anchor and thrust blocks shall be constructed at the locations, to the
size and of the materials as specified on the drawings.

JOINTS AND CONNECTIONS

All joints and connections shall be constructed to withstand the design
working pressure for the pipeline without leakage and shall leave the
inside of the pipeline free of any obstruction which could reduce the
pipe capacity below design requirements.

All fittings, such as couplers, reducers, bends and tees shall be made
of material that is recommended for use with the type of pipe specified
and shall be installed in accordance with the recommendations of the
pipe manufacturer. All fittings, field welds and bare pipe shall be
covered with a coating equal in quality to that specified for the pipe.

A dielectric coupler (insulator) shall be installed between pipes with
different coatings, different materials and different ages.

CATHODIC PROTECTION

When cathodic protection is specified on the drawings the pipe shall be
protected with sacrificial galvanic anodes.

MATERIALS

Pipe shall equal or exceed the requirements listed in one of the
following standards:

ASTM A 760 Pipe, Corrugated Steel, Zinc Coated

Federal Specification WW-P-402C Pipe, Corrugated (Aluminum Alloy Amend.
1)

Federal Specification WW-P-405B Pipe, Corrugated Iron or Steel, Zinc
Coated (Amend. 1)

AASHTO M 36 Zinc Coated (Galvanized) Corrugated Iron or Steel Culverts
and Underdrains

AASHTO M 196 Corrugated Aluminum Alloy Culverts and Underdrains (Amend.
AASHTO 196)

AASHTO M 245 Precoated, Galvanized Steel Culverts and Underdrains

AASHTO M 257 Steel Sheet, Aluminum Coated (Aluminum Type II) by the Hot
Dip Process for Sewer & Drainage Pipe

Pipe bands or couplers shall meet the requirements of the applicable
pipe specification, except that no flange (channel), smooth slab or
dimple band shall be used.

Gaskets shall meet the requirements of ASTM C 443.

VALVES AND APPURTENANCES

Pipeline valves and appurtenances shall be of the size, type, material
and pressure rating as shown on the drawings.

TESTING

When water is available at the time the pipe is installed the system
shall be given an operational test. This test shall consist of filling
the pipe with water, taking care to bleed of any air in the pipe. All of
the system components shall operate without difficulty. Leakage or
defects caused by poor materials or workmanship shall be replaced or
repaired. When water is not available to complete a test, the installer
shall provide a guarantee stating they will return and fix leaks that
are found when the pipe is initially filled with water.

GUARANTEE

The installing Contractor shall certify that the installation conforms
to the requirements of this specification and furnish a written
guarantee protecting the landowner against defective materials and
workmanship for a period of less not than 1 year. The guarantee will
identify manufacturer of pipe and pipe markings.

ADDITIONAL SPECIFICATIONS

FIGURE 1

> TRENCH WIDTH AND BACKFILL REQUIREMENTS
>
> NATURAL GROUND
>
> FINAL BACKFILL
>
> 6" FINAL BACKFILL
>
> (Maximum particle size 1 inch)
>
> INITIAL BACKFILL

OD (Compacted select

0.7 OD 4" bedding materials)

> 9 inches minimum
>
> (If Necessary)
>
> TYPICAL TRENCH DETAIL
>
> 5 FT DEPTH, MAXIMUM
>
> NATURAL GROUND
>
> 1
>
> FINAL BACKFILL \*\*
>
> FINAL BACKFILL
>
> (Maximum particle
>
> size 1 inch)

OD

0.7 OD INITIAL BACKFILL

> (Compacted select
>
> bedding materials)
>
> 4" (If Necessary) 9 inches minimum
>
> ALTERNATIVE TRENCH DETAIL

DEPTH GREATER THAN 5 FEET

> \*\* Slope typically varies from ¾ to 1/1/2:1 or greater based upon
>
> material classification and other factors such as wetness, vibration,
>
> surcharge, etc. Refer to OSHA Subpart P for details.