**NATURAL RESOURCES CONSERVATION SERVICE\
CONSTRUCTION SPECIFICATION**

**CORRUGATED METAL PIPE CONDUIT INSTALLATION**

1\. SCOPE

The work shall consist of furnishing and placing circular, arched or
eliptical corrugated metal pipe and the necessary fittings as shown on
the plans. This specification does not cover pipe designed for pressure
flow.

2\. MATERIALS

Zinc-coated, aluminum coated or aluminum-zinc alloy coated iron or steel
corrugated pipe and fittings shall conform to the requirements of ASTM
Specification A-760 for the specified type of pipe, and to the following
additional requirements:

a\. The sheet thickness, and the corrugation type and nominal size shall
be as shown on the drawings.

b\. Unless otherwise specified, circumferential shop riveted seams shall
have a maximum rivet spacing of 6 inches, except that 6 rivets will be
sufficient for 12-inch diameter pipe.

c\. When close riveted pipe is specified: (1) the pipe shall be
fabricated so that the rivet spacing in the circumferential seams shall
not exceed 3 inches, except that 12 rivets will be sufficient to secure
the circumferential seams in 12-inch pipe, and (2) in those portions of
the longitudinal seams that will be covered by the coupling bands, the
rivets shall have finished flat heads or the rivets and holes shall be
omitted and the seams shall be connected by welding to provide a minimum
of obstruction to the seating off the coupling bands.

d\. Double riveting or double spot welding of pipe less than 42 inches
in diameter may be required. If specified, the riveting or welding shall
be done in the manner specified for pipe 42 inches or greater in
diameter.

e\. When specified, caulked seam corrugated metal pipe shall conform to
the following additional requirements:

\(1\) Caulked seam corrugated metal pipe shall have all circumferential
and horizontal seams caulked with an asphalt compound before riveting.
This shall be accomplished by applying a uniform bead (1/4) inch minimum
diameter) of the asphalt compound to the inner lap surface before
riveting, such that when the rivets are in place, all voids are filled
and a coating of asphalt is between the lap surfaces.

\(2\) The asphalt compound shall consist of an asphalt base combined
with inert filler material to form a heavy-bodied compound that will not
sag or run out of the seam. The compound shall contain 63 to 68 percent
solids by weight. It shall be similar in type and equal in quality to
Trumbull 5W Asphalt Mastic, knife grade, as manufactured by the Trumbull
Asphalt Company of Delaware.

3\. HANDLING THE PIPE

The contractor shall furnish such equipment as is necessary to place the
pipe without damaging the pipe or coating. The pipe shall be transported
and handled in such a manner as to prevent bruising, scaling or breaking
of the spelter coating or bituminous coating.

4\. REPAIR OF DAMAGED COATINGS

Breaks or scuffs on bituminous coatings that are less than 36 square
inches in area shall be repaired by the application of two coats of hot
asphaltic paint or a coating of cold-applied bituminous mastic. The
repair coating shall be at least 0.05 inches after hardening and shall
bond securely and permanently to the pipe. The material shall meet the
physical requirements for the original coating. Whenever individual
breaks exceed 36 square inches in area or when the total area of breaks
exceeds 0.5 percent of the total surface area of the pipe, the pipe will
be rejected.

5\. LAYING AND BEDDING THE PIPE

Unless otherwise specified, the pipe shall be installed in accordance
with the manufacturer\'s recommendations. The pipe shall be laid with
the outside laps of circumferential joints pointing upstream and with
longitudinal laps at the sides at about the vertical midheight of the
pipe. Field welding of corrugated galvanized iron or steel pipe will not
be permitted. Unless otherwise specified, the pipe sections shall be
joined with water-tight coupling bands, with a minimum width of 12
inches, or flanges for a flange-type connection. The area between pipe
and coupling band shall be coated with either an asphalt cement to
insure a water-tight joint or a rubber neoprene gasket 3/8 inch thick
and as wide as the connecting band + 1 inch.

The trench or foundation width in or on which the pipe will be laid
should be at least: (1) 2 times the pipe diameter, or (2) the pipe
diameter plus 2 feet, whichever is the greater.

Pipe should be laid on a moist, compacted foundation (not wet nor hard
and dry). Just before the pipe is laid, spread a 2 to 3 inch layer of
moist loose soil for the pipe to be placed on. The pipe should make
uniform contact with the soil along its entire length.

Perforated pipe shall be laid with perforations down and oriented
symmetrically about a vertical centerline. Perforations shall be clear
of any obstructions at the time the pipe is laid.

6\. BACKFILLING

The pipe shall be loaded sufficiently during backfilling around the side
to prevent its being lifted from the bedding.

Backfill around the pipe shall be placed in layers not more than 6
inches thick before compaction. Each layer of backfill shall be
compacted with power tampers or hand tamping to a greater density than
the surrounding undisturbed soil. Backfill over and around the pipe
shall be brought up uniformly on all sides and shall extend a minimum of
2 feet over the pipe before earth embankment with earth moving equipment
over the pipe is started. Special care shall be taken not to disturb the
grade and alignment during backfill operations.

7\. ADDITIONAL ITEMS WHICH APPLY TO THIS JOB