UNITED STATES DEPARTMENT OF AGRICULTURE

Rural Utilities Service

**BULLETIN 1751F-641**

**SUBJECT: [Construction of Buried Plant]{.underline}**

**TO:** All Telecommunications Borrowers

RUS Telecommunications Staff

**EFFECTIVE DATE:** Date of Approval

**EXPIRATION DATE:** Seven years from effective date

**OFFICE OF PRIMARY INTEREST:** Outside Plant Branch, Telecommunications
Standards Division

**PREVIOUS INSTRUCTIONS:** This bulletin replaces REA Telephone
Engineering & Construction Manual (TE&CM) Section 641, Construction of
Buried Plant, Issue 4, dated April 1973.

**FILING INSTRUCTIONS:** Discard REA Telephone Engineering &
Construction Manual (TE&CM) Section 641, Construction of Buried Plant,
Issue 4, dated April 1973, and replace it with this bulletin. File with
7 CFR 1751 and is available to RUS staff on RUSNET.

**PURPOSE:** This bulletin provides RUS borrowers, consulting engineers,
contractors and other interested parties with information concerning the
construction of buried plant facilities.

Adam Golodner 06/30/95

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Administrator Date

**TABLE OF CONTENTS**

1\. General
\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\... 6

2\. Supervision of Construction \...\...\...\...\...\...\...\...\.... 7

3\. Characteristics of Tractors \...\...\...\...\...\...\...\...\... 13

4\. Characteristics of Plowing Equipment \...\...\...\...\...\... 15

5\. Capabilities of Tractors and Plows \...\...\...\...\...\..... 17

6\. Handling and Care of Materials During Construction \.... 18

7\. Repair of Cables or Wires Damaged During Construction . 19

8\. Preparation for Splicing or Termination \...\...\...\...\... 20

9\. Installation Procedures for Filled Cables in

Cold Weather \...\...\...\...\...\...\...\...\...\...\...\...\...\... 21

10\. Assembly Units
\...\...\...\...\...\...\...\...\...\...\...\...\.... 22

11\. Directional Boring \...\...\...\...\...\...\...\...\...\...\...\...
22

12\. Figure Eighting Cable \...\...\...\...\...\...\...\...\...\...\...
22

13\. Aerial Inserts
\...\...\...\...\...\...\...\...\...\...\...\...\.... 23

14\. Numbering and Identification \...\...\...\...\...\...\...\..... 23

15\. Acceptance Testing \...\...\...\...\...\...\...\...\...\...\...\...
23

**TABLES & FIGURES**

Figure 1 Typical Cable or Wire Plowshare with Fixed Feed

Tube\...\...\...\...\...\...\...\...\...\...\...\...\...\...\.... 25

Figure 2 Plowshare with Vertical Shin \...\...\...\...\...\...\... 26

Figure 3 Plowshare with Shin Angled Back From Plow-Point .. 27

Figure 4 Plowshare with Shin Angled Toward Plow-Point \..... 28

Figure 5 Plowshare with Hinged Feed Tube \...\...\...\...\...\... 29

Figure 6 Plowshare with Floating Feed Tube \...\...\...\...\.... 30

INDEX:

Outside Plant

Construction

Telecommunications

**ABBREVIATIONS**

AWG American Wire Gauge

BFC Buried Filled Cable Assembly Unit

BFO Buried Filled Fiber Optic Cable Assembly Unit

°C Degrees Celsius

CATV Community Antenna Television

CFR Code of Federal Regulations

°F Degrees Fahrenheit

LD Loan Design

NESC National Electrical Safety Code

R/W Right-of-way

REA Rural Electrification Administration

RUS Rural Utilities Service

TE&CM Telecommunications Engineering and Construction Manual

**DEFINITIONS**

**[BFC]{.underline}:** A buried filled cable assembly unit which
includes all the material and labor costs to place, plow, and/or trench
and backfill 1,000 feet (304.8 meters) of filled buried copper cable.

**[BFO]{.underline}:** A buried filled fiber optic cable assembly unit
which includes all the material and labor costs to place, plow and/or
trench and backfill 1,000 feet (304.8 meters) of filled buried fiber
optic cable.

**[Construction Drawings]{.underline}:** The drawings developed through
the staking process and used to guide the construction of outside plant
facilities.

**[Drawbar Pull]{.underline}:** The effective pulling force delivered.

**[Feed Tube]{.underline}:** A tube attached to the blade of a plow
which guides and protects the cables or wires as they enter the earth.
There are several types of feed tubes.

**[Figure Eighting]{.underline}:** A method of removing cable or wire
from a reel and forming the removed cable or wire in the shape of the
numeral eight.

**[Fixed Feed Tube]{.underline}:** A feed tube permanently attached to
the plow; it may have a removable back plate.

**[Floating Feed Tube]{.underline}:** A feed tube attached to a plow so
relative motion may occur between the feed tube and the plow around axes
that are essentially vertical and horizontal (perpendicular to direction
of travel).

**[Fuse Link]{.underline}:** A fine gauge section of cable or wire that
serves as a fuse (that is, open-circuits to interrupt the current should
it become excessive) that coordinates with telecommunications cable and
wire plant, and telecommunications protective devices.

**[Hinged Feed Tube]{.underline}:** A feed tube attached to a plow so
relative motion may occur between the feed tube and the plow around an
essentially vertical axis.

**[Loan Design]{.underline}:** A comprehensive engineering plan for a
project used to support a loan application to the Rural Utilities
Service (RUS).

**[Static Plow]{.underline}:** A plow that depends upon drawbar pull
only for its movement through the soil.

**[Type H Outside Plant Housing]{.underline}:** A housing consisting of
an upper cover and a base cover. The upper cover consists of a top,
front and back plate with the front cover removable to permit entry. The
base cover consists of a front and back plate. The base cover back plate
can be an extension of the upper back plate cover.

**[Type M Outside Plant Housing]{.underline}:** A housing consisting of
a one piece upper sleeve designed to fit over the base cover trapping
air to prohibit water from entering the splice area.

**[Resident Engineer]{.underline}:** The representative of the Engineer
who is delegated full-time \"on-site\" engineering responsibilities for
construction administration.

**[Right-of-Way]{.underline}:** The strip of land over which facilities
such as highways, railroads, power lines, other utilities, or
telecommunication lines are constructed.

**[RUS accepted (material and equipment)]{.underline}:** Material and
equipment which RUS has reviewed and determined that:

a\. Final assembly is conducted within the United States, Mexico, or
Canada or any of their respective territories and the cost of United
States, Mexican, or Canadian, manufactured components, in any
combination, is more than 50 percent of the total cost of all components
utilized in the material or equipment, and

b\. The material or equipment complies with pertinent RUS or industry
standards and field experience has demonstrated that the material or
equipment is suitable for use on systems of RUS telecommunications
borrowers.

**[RUS technically accepted (material and equipment)]{.underline}:**
Material and equipment which RUS has reviewed and determined that:

a\. Final assembly is not conducted within the United States, Mexico, or
Canada, or any of their territories, or the cost of components within
the material or equipment which are manufactured within the United
States, Mexico, or Canada, or any of their territories, cost 50 percent
or less than the total cost of all components utilized in the material
or equipment, and

b\. The material or equipment complies with pertinent RUS or industry
standards and field experience has demonstrated that the material or
equipment is suitable for use on systems of RUS telecommunications
borrowers.

**[Supervision]{.underline}:** The responsibility of the resident
engineer or the resident engineer\'s assigned inspector to observe the
contractor\'s employees installing cable, outside plant housings,
splices, clean-up, and other related work items associated with the
construction project.

**[Vibratory Plow]{.underline}:** A plow utilizing induced periodic
motion of the blade in conjunction with drawbar pull for its movement
through the soil.

**1. GENERAL**

**1.1** This bulletin discusses construction of buried plant facilities
using filled copper cables or wires, and filled fiber optic cables. The
information and recommendations in this bulletin are advisory.

**1.2** Some of the work items associated with buried plant construction
are as follows:

a\. Pre-installation inspection of copper cables and wires

and fiber optic cables;

b\. Plowing or trenching of copper cables and wires and

fiber optic cables;

c\. Lateral trenching of copper cables and wires and fiber

optic cables to outside plant housings or poles;

d\. Installation of outside plant housings;

e\. Installation of serving area interface cabinets;

f\. Tamping of trenches;

g\. Installation of direct buried filled splice cases for

copper cables and wires and fiber optic cables;

h\. Splicing of copper cables and wires and connection of

shield bonds and related grounding;

i\. Splicing of fiber optic cables and connection of armor

bonds and related grounding;

j\. Installation of filled buried service wires;

k\. Terminating of filled buried service wire directly to

cable conductors;

l\. Construction of aerial inserts;

m\. Placement of filled terminal blocks in outside plant

housings in high service order activity locations;

n\. Placement of load coils (See Note);

o\. Placement of digital carrier repeater housings, and

lightwave repeater housings;

Note: When loaded lines are determined by RUS to be economically
feasible and the overall system design complies with the Modernization
Plan (7 CFR 1751, Subpart B).

p\. Placement of directional route and warning markers,

and route and terminal numbers on outside plant

housings; and

q\. Conducting acceptance tests.

**1.3** Information for the design, staking, splicing, acceptance
testing, and construction of direct buried plant can be found in the
following Rural Utilities Service (RUS) documents:

a\. RUS Form 515, RUS Telephone System Construction Contract

(Labor and Materials);

b\. RUS Bulletin 345-150, Specifications and Drawings for

Construction of Direct Buried Plant (RUS Form 515a);

c\. RUS Bulletin 345-153, Specifications and Drawings for

Construction of Pole Lines, Aerial Cables and Wires

(RUS Form 515f);

d\. RUS Bulletin 345-63, RUS Standard for Acceptance Tests

and Measurements of Telephone Plant (PC-4);

e\. RUS Bulletin 1751F-640, Design of Buried Plant -

Physical Considerations;

f\. RUS Bulletin 1751F-642, Construction Route Planning of

Buried Plant; and

g\. RUS Bulletin 1753F-401(PC-2), RUS Standard for Splicing

Copper and Fiber Optic Cables (codified under 7 CFR

1755.200).

**2. SUPERVISION OF CONSTRUCTION**

**2.1** The construction of buried plant facilities should be closely
supervised because of the rapid rate at which plowing or trenching
proceeds and because the cable or wire cannot be visually inspected
after installation. This close supervision should be accomplished by
having the resident engineer or resident engineer\'s assigned inspector
present at all times during the buried plant construction operation. The
resident engineer or the resident engineer\'s assigned inspector also
has the responsibility to ensure that the correct pair sizes, gauges,
and types of copper cables or wires, and the correct number of optical
fibers, type of optical fibers and types of fiber optic cables are
placed at the correct depths and locations within the right-of-way
(R/W), and are free of damage during the buried plant construction
operation.

**2.2** When more than one plowing or trenching operation is being
performed at the same time, each plowing or trenching operation should
be supervised. During the installation of the cables or wires,
construction may be stopped pending the resident engineer\'s decision
concerning proposed changes in the construction route from that shown on
the construction drawings. Undue delays in making such decisions are
costly to the borrower and should be avoided.

**2.3** Cables or wires should be inspected for damage after
installation. In order to perform this inspection, the plow should be
advanced 10 feet (3.05 meters) past an outside plant housing location
and stopped. A length of cable or wire should then be pulled through the
plow\'s feed tube, back through the slot and over to the outside plant
housing. This procedure provides an opportunity to inspect short lengths
of cables or wires for damage. Particular care should be exercised in
bending the cables or wires during this inspection procedure.

**2.4** The minimum bending radius for copper cables and wires should
not be less than 10 times the outside diameter of the copper cable or
wire. The minimum bending radius for fiber optic cables should not be
less than 20 times the outside diameter of the fiber optic cable. If
cables or wires are bent too sharply, damage could occur to the copper
conductors, optical fibers, shields, armors, and/or jackets of the
cables or wires.

**2.5** All reels of filled copper cable and wire and all reels of
filled fiber optic cable should be inspected before installation for
visual signs of damage. In addition, filled copper cable and wire ends
and filled fiber optic cable ends should be sealed to prevent moisture
entry into the cores of copper cables and wires and fiber optic cables
during transportation, in storage, and during placement.

**2.6** The buried plant construction route should be inspected before
beginning the plowing or trenching operation. When selecting the buried
plant construction route, the convenience and ease of installation
should be considered providing the quality of construction, which would
affect future operation and maintenance of the telecommunications
system, is not decreased and construction costs to the borrower are not
substantially increased.

**2.7** Cables and wires, as well as, the equipment and procedures
should be continuously inspected during the installation to prevent
damage to the cables and wires and to ensure that proper depths are
maintained at all times. Caution should be exercised to prevent damage
to the cables and wires because of cable or wire slippage in the ground
as the plow or trencher leaves the starting pit. Cables and wires should
be checked for damage at sudden or severe changes in grade or where the
plow or trencher is violently impaired in movement (such as striking a
large rock). Generally, buried plant facilities are more susceptible to
damage during trenching operations and backfilling than they are when
being plowed into the ground. The resident engineer should make certain
that the cables or wires are properly installed in open trenches, that
the trenches are properly backfilled, and that the surfaces of the
ground are restored to the previous conditions. Lateral trenches should
be backfilled and tamped where necessary to provide solid bases for the
cables or wires to rest upon between the plow slots and the outside
plant housings. At outside plant housing locations, the soil should be
properly tamped so that it will conform to the cables or wires bending
radii. If this procedure is not followed, the cables or wires may sag
downward from the attachments within the outside plant housings as the
soil settles resulting in possible damage to the copper conductors,
optical fibers, and/or loss of cable or wire shield or armor continuity.
All trenches should be promptly backfilled with soil and mechanically
tamped so that the soil is restored to its original grade to ensure that
future settlement does not result in a hazard to vehicular, animal, or
pedestrian traffic. In areas where experience indicates that water added
to the backfill (flooding) does help achieve compaction, (usually in
sandy soil), the flooding method may be used as an alternative method to
mechanical tamping. Unprotected and unmarked trenches should not be left
open overnight.

**2.8** Construction work should be organized so that plowing and/or
trenching operations, together with the placement of cables or wires,
service wires, outside plant housings, and other associated functions
are be done concurrently. In this manner, the interval from start to
completion of any section of the project is held to a minimum. The
resident engineer assigned to each buried plant construction operation
may not have time to inspect all the details of related work being
performed along the construction route. Therefore, the resident engineer
should have additional personnel to supervise and inspect all such
construction. The number of supervisory personnel required to inspect
all aspects of construction depends on the amount of proposed
construction and on the number of different operations being performed
simultaneously.

**2.9** Installation of reel-end splices which may change proposed
digital carrier or lightwave repeater locations should be considered for
re-routing. Because of the limited deviations allowed in digital carrier
or lightwave repeater spacings, all repeatered lines should be
constructed first, starting at the central office and advancing in the
direction of the repeatered line with a continuous operation to the last
repeater point on each repeatered section unless otherwise specified in
the contract. Deviations from this procedure should be approved in lieu
of holding up the construction project in the event of late cable or
wire deliveries, or R/W difficulties, etc.

**2.10** Installation of reel-end splices on loaded lines (See Note on
Page 6) which may change proposed load coil locations should be
considered for re-routing. Because of the limited deviations allowed in
load coil spacings, all loaded lines should be constructed first,
starting at the central office and advancing in the direction of the
loaded line with a continuous operation to the last load point on each
loaded section unless otherwise specified in the contract. Deviations
from this procedure should be approved in lieu of holding up the
construction project in the event of late cable or wire deliveries, or
R/W difficulties, etc.

**2.11** Sequential markings on the outer jackets of cables and wires
are provided to facilitate proper spacing of digital carrier or
lightwave repeater housings, load coils (when loaded lines are
determined by RUS to economically feasible and the overall system design
complies with the Modernization Plan \[7 CFR 1751, Subpart B\]), and
inventory of cable and wire units. The resident engineer and the
contractor should agree on the inventory of buried plant units as they
are installed. Construction drawings should be appropriately marked so
they can be used as permanent records of all plant items.

**2.12** Road and ground surfaces should be inspected to determine if
the surfaces have been damaged by the plowing or trenching equipment. If
the surfaces have been damaged, the surfaces should be repaired and
reinspected to determine that the surfaces have been properly repaired.
If repairs are necessary, the repairs should be performed in accordance
with Federal, State, or local codes, and as set forth in RUS Form 515,
RUS Telephone System Construction Contract.

**2.13** Outside plant housings should be inspected during construction
to determine that:

a\. The correct size and sealer have been properly

installed;

b\. Copper cable or wire conductors have been correctly

terminated;

c\. Shields and/or armors of copper cable or wire have been

bonded and grounded;

d\. Cables or wires tags have been marked with the proper

information per RUS Bulletin 1753F-401(PC-2);

e\. Correct routes and outside plant housing numbers, and

warning decals have been installed;

f\. Stakes or stub poles have been installed at the

proper depths; and

g\. Rodent protection has been properly installed,

as required.

**2.14** Direct buried filled splices and cases should be inspected
during construction to ensure that:

a\. Cable or wire jackets have been properly prepared;

b\. Copper cable or wire conductors have been properly

spliced;

c\. Optical fibers have been properly spliced;

d\. Buffer tubes containing the optical fibers have a

sufficient amount of slack;

e\. Shields and/or armors of cables or wires have been

bonded and grounded;

f\. Encapsulating compounds have been properly mixed and

applied; and

g\. The direct buried filled splice cases have been

properly installed.

**2.15** When direct buried filled splice cases are required to be
protected from mechanical damage, protection of the splice cases should
be accomplished either by placing treated planks approximately 6.0
inches (152 millimeters) above the splice cases or by placing the splice
cases in handholes.

**2.16** Construction drawings should be accurately marked to indicate
the following:

a\. Routing of cables or wires;

b\. Lengths, pair sizes, gauges, and types of copper cables;

c\. Lengths, number and types of optical fibers, and types

of fiber optic cables;

d\. Locations of direct buried filled splice cases and

splice warning signs;

e\. Locations of handholes;

f\. Locations of outside plant housings;

g\. Locations of warning and route signs;

h\. Locations of load coils (See Note on Page 6);

i\. Locations of digital carrier repeater and serving area

interface cabinets;

j\. Locations of lightwave repeater housings; and

k\. Locations of other buried utilities and obstacles.

This should facilitate future reinforcements which may be required on
the project. If depths greater than normal depths in the Loan Design
(LD) have been specified to facilitate future reinforcing or to provide
a greater degree of mechanical protection to the buried plant
facilities, the resident engineer should make certain that such depths
are achieved.

**2.17** For copper cable buried construction projects, direct buried
filled splice cases, trenching, labor, and other materials associated
with the installation of reel-end splices are included in the BFC
assembly unit. Therefore, such splice cases are not covered in the final
inventory for compensation purposes. Although the splice cases are not
inventoried, all splices cases and cable or wire lengths should be shown
on the construction drawings for future reference. For ease of future
location, all direct buried filled splices should be located at a
measured distance with respect to the center of the road or from some
other permanent marker such as a locating ball, etc. Construction
drawings should also indicate the location of all outside plant housings
or direct buried filled splice cases that were installed for the purpose
of repairing cable or wire damage that occurred during construction.

**2.18** For fiber optic cable buried construction projects, the BFO
assembly unit does not include direct buried filled splice cases,
trenching, labor, and other materials associated with the installation
of reel-end splices. Therefore, such splice cases should be covered in
the final inventory for compensation purposes. All splice cases and
cable lengths should be shown on the construction drawings for future
reference. For ease of future location, all direct buried filled splices
should be located at a measured distance with respect to the center of
the road or from some other permanent marker such as a locating ball,
etc. Construction drawings should also indicate the location of all
outside plant housings or direct buried filled splice cases that were
installed for the purpose of repairing cable damage that occurred during
construction.

**2.19** Where rock conditions exist that make the plowing of cables or
wires impractical or inadvisable, trenching, aerial inserts, or
re-routing should be considered as construction options along that
particular section of the route. The decision as to what option should
be used is normally made during the construction period by the resident
engineer.

**2.20** The buried construction route should be cleared only to a width
that will allow for the passage of the cable or wire placing equipment.
The responsibilities in regards to obtaining, operating on, clearing
obstructions (trees, brush, etc.), disposal of debris and restoration of
public and private R/W, including any compensations are defined in RUS
Bulletin 345-150, Specifications and Drawings for Construction of Direct
Buried Plant (RUS Form 515a).

**2.21** Special care should be exercised to avoid damage to fences,
trees, lawns, and shrubs. Disturbance of ground surfaces by heavy
construction equipment should be kept to a minimum. All fences removed
or cut for access of the equipment should be repaired promptly in
accordance with RUS Bulletin 345-150, Specifications and Drawings for
Construction of Direct Buried Plant (RUS Form 515a). When installing
cables or wires in pasture and/or range lands, gates should be closed
and fence openings should be repaired as soon as possible.

**2.22** Plowing or trenching operations within the area of subsurface
structures should be carried out in a manner that will avoid accidental
contact of the digging tools with such structures. The equipment which
may be used for such operations should be operated only by qualified
personnel. When foreign structures are encountered such as buried power
cables, Community Antenna Television (CATV) cables, gas lines, etc., the
installation of the buried telecommunications cables or wires should be
performed in accordance with the requirements of the latest edition of
the National Electric Safety Code (NESC) or Federal, State, or local
codes. [Where Federal, State, or local codes are more stringent than the
NESC, the installation of the buried telecommunications cables or wires
should be performed in accordance with the more stringent
codes]{.underline}.

**2.23** The minimum depth requirements for buried cables or wires are
given in RUS Form 515 and RUS Bulletin 345-150 (RUS Form 515a). In
certain situations it may be desirable to bury cables or wires at depths
greater than the minimum depths given in RUS Form 515 and RUS Bulletin
345-150 (RUS Form 515a). These greater depths need to be approved by RUS
prior to bidding.

**2.24** Portions of the filled buried service wires that are exposed to
possible subscriber damage should be protected by placing the exposed
portions of the wires in nonmetallic conduits or split \"U\" guards.

**3. CHARACTERISTICS OF TRACTORS**

**3.1** The resident engineer should be familiar with the
characteristics and capabilities of the tractors and plowing equipment
used in the construction of buried cable or wire plant facilities. The
equipment used on the construction project should be subjected to the
requirements listed in RUS Form 515 and RUS Bulletin 345-150 (RUS Form
515a) and approval of the public authorities having jurisdiction over
highway and road R/W. The size and maneuverability of the equipment
should also be considered in the selection of the cable or wire
construction route.

**3.2** The power capabilities of static type tractors may be stated in
either terms of drawbar horsepower or drawbar pounds pull. Direct gear
drive tractors are normally rated in terms of drawbar horsepower and
tractors with torque converters are normally rated in terms of drawbar
pounds pull at a given forward speed. The terms drawbar horsepower and
drawbar pounds pull refer to the reserve tractive horsepower and the
reserve tractive force, respectively, available beyond that required to
move the tractor itself. Crawler and rubber-tired tractors are two types
of static tractors.

**3.3** In crawler tractors, the factors which influence traction are
the width and length of the track and the design of the grousers.
Grousers are metallic ribs which are attached to the tracks to penetrate
and grip the soil. The grousers are attached to the tracks at right
angles to the tracks and to the direction of motion. Grousers are used
to ensure that traction is obtained by shearing the soil and not by
friction of the metal on the soil alone. In general, crawler tractors
with long, wide tracks and high grousers obtain greater traction than
crawler tractors with short, narrow tracks and low grousers.

**3.4** Factors influencing the traction of rubber-tired tractors
include the weight and weight distribution of the tractor, tire size,
inflation pressure and tread pattern, and wheel base.

**3.5** For traction in various soils, a choice of various widths,
lengths, and depths of track may be obtained on crawler tractors. For
rubber-tired tractors, the traction in various soils will depend on
sizes and inflation pressures of the tires. Both crawler and
rubber-tired tractors may be operated in surface conditions varying from
solid rock to swamp-like soils and weather conditions varying from
droughts to floods and from frosts to summer sun.

**3.6** Manufacturers of both crawler and rubber-tired tractors should
be contacted to determine the tractive forces of their respective
equipment in various soil conditions.

**3.7** Rubber-tired tractors are more difficult to keep on straight
courses, particularly on slopes, than crawler tractors. Factors which
can influence the steering of rubber-tired tractors are the tractor\'s
transmission type and steering mechanism. Rubber-tired tractors can be
manufactured with clutch-brake, differential and limited slip
differential transmissions. Steering of clutch-brake rubber-tired
tractors is accomplished by the skidding of the wheels. Steering
rubber-tired tractors with differential drive transmissions is
accomplished with steerable wheels at the front, at the back, or all
around.

**3.8** If rubber-tired tractors are used for the construction project,
all-wheel drive tractors with all wheel steering and limited slip
differential transmissions should be the preferred rubber-tired tractor
types because the oblique steering properties tend to offset any
tendency of the tractors to slip sideways on the slopes. It should be
noted that rubber-tired tractors having rear wheel steering are
difficult to keep on straight courses when the plow is in the ground.

**3.9** Cables or wires are usually installed along the most feasible
route, whether it is along public R/W, private R/W, or across farming or
grazing lands. Farming or grazing landowners are usually reluctant to
consent to the use of crawler or rubber-tired tractors on farming or
grazing lands because of the surface damage that can be done to the
farming or grazing lands as a result of these type tractors. Since
crawler tractors do far less surface damage than rubber-tired tractors,
crawler tractors should be the preferred tractors for buried plant
construction projects involving private R/W across farming or grazing
lands.

**3.10** Department of transportation officials frown upon surface
damage done to hard highway or road surfaces as a result of track
slippage. Since track slippage can result from the crawler\'s
insufficient power and traction (weight), either rubber-tired tractors
or crawler tractors with rubber pads should be the preferred tractors
for buried plant construction projects involving hard surfaces because
the rubber-tired tractors and the rubber padded crawler tractors do not
damage the hard surfaces of the public or private R/W.

**3.11** The drawbar pull characteristics of static type tractors are
not entirely applicable to vibratory tractors. The vibratory tractor\'s
principle of cutting and vibrating can reduce the drawbar pull, as
related to static type tractors, as much as 80 percent in some soil
conditions. In addition, since the vibratory tractor\'s weight is
dictated by drawbar requirements and not engine size, a significant
reduction in the vibratory tractor\'s weight and size can be achieved
through plow vibrations. However, drawbar requirements for vibratory
type tractors increase as the plowing speeds increase and, therefore to
obtain full advantage of plow vibrations, plowing speeds are relatively
low. Thus for a vibratory tractor\'s drawbar capability, a vibrating
plow should settle to a speed that depends on the soil conditions.

**4. CHARACTERISTICS OF PLOWING EQUIPMENT**

**4.1** The soil properties such as hardness, friction, adhesion,
cohesion, and abrasion should be evaluated before selecting the type of
plow for the construction project. Soil hardness is the resistance to
penetration. Soil hardness is at a minimum for sandy soil and at a
maximum for dry clay. Friction is the force at the plow/soil interface
that resists the motion or tendency to motion of the plow to the soil.
Friction is affected by the amount of moisture and natural lubricants in
the soil. Adhesion is the sticking of the soil to the plow being used.
Cohesion is the resistance of the soil to tearing apart and it is at its
maximum in clay soil. Abrasion is the property of wearing away of the
plowing equipment by the soil particles.

**4.2** Static and vibratory type tractors can be equipped with either
direct mounted or towed plows. One advantage in using towed plows over
direct mounted plows is that the tractors can be of the general purpose
type. Towed plows can also be unhitched for crossing soft patches of
soil, swamps, and streams and winched across these areas with the
tractors standing on firm ground. When undulating terrain is
encountered, towed plows in some instances can do better jobs of
installing the cables or wires at the proper depths than some of the
direct mounted plows. However, direct mounted plows are considered
superior to towed plows for most terrain and soil conditions. One of the
reasons that direct mounted plows are considered superior to towed plows
is that the direct mounted plows can be easily maneuvered. Another
reason is that direct mounted plows rely on the weight of the tractor
and its hydraulics for positive holddown rather than the dead weights
used for towed plows. The dead weights placed on towed plows to maintain
a 15,000 pound (67,723 newton) downward force may result in a reduction
of the tractor\'s power necessary for plowing. With properly designed
direct mounted plows, the proper depths of the cables or wires can be
maintained.

**4.3** Direct mounted plows are considered more stable than towed plows
because the towbars of the tractors pulling the separately mounted plows
tend to lift the fronts of the tractors off the ground. For tractors
equipped with towed plows, the stability of the tractor increases as the
tractor\'s weight is increased but decreases as the drawbar pull
increases. For tractors with direct mounted plows, the stability of the
tractor increases as the drawbar pull increases and the resistance
offered by the earth to the plow increases.

**4.4** The ideal plow should be designed so that the cables or wires
exit the plowshare at approximately the same heights above the bottoms
of the plowed slots regardless of the depths. The disadvantage of these
type plows are that the cables or wires may be damaged because of abrupt
changes in elevation when passing over rocks, etc. One method of
overcoming this type of cable or wire damage is the use of four point or
parallelogram type linkage.

**4.5** If hydraulic rams are used to transmit part of the tractor\'s
weight to the plow for positive holddown, the hydraulic rams should be
double acting and capable of raising the rear of the tractor with the
plow-point resting on the ground.

**4.6** The equipment should be capable of extending the plow blade to a
depth of at least 36 inches (914 millimeters) when the tractor is
angling across and along drainage ditches or rough terrain. The
plow-point, leading-edge (shin), share-shape, and share-width should be
designed to cut a narrow slot through the earth without excessively
disturbing the soil. The broad \"V\" shaped leading-edge (shin) equal to
the plowshare\'s thickness has been found to be satisfactory. Figure 1
depicts a sketch of a typical cable or wire plowshare. The proportions
and the angles of attack of the plow-points have been shown to have the
greatest effect on drawbar pull and pull-down. This means that plows
designed with vertical shins as shown in Figure 2 or shins that angle
back from the plow-points as shown in Figure 3 tend to stay in the
ground better than plows designed with shins angled towards the
plow-points as shown in Figure 4. For most soils and rock, the
plow-point penetration angles should range from a minimum of 30° to a
maximum of 50° from the horizontal. In addition to plowshares with fixed
feed tubes as shown in

Figure 1, plowshares are also available with either hinged or floating
feed tubes. Figure 5 shows a plowshare with a hinged feed tube, while
Figure 6 shows a plowshare with a floating feed tube.

**5. CAPABILITIES OF TRACTORS AND PLOWS**

**5.1** One tractor should be able to pull a plow through most soil
types. A second tractor to assist the prime tractor should be used when
additional traction is needed in hard to plow soil types, muddy and
swampy type soils, or other difficult areas. Crawler tractors generally
provide better flotation and more positive traction than rubber-tired
tractors. The prime tractor used to pull the plow should be the larger
of the two tractors. The prime tractor should have a minimum rating
equivalent to 55,000 pounds (2.45 x 105 newtons) drawbar pull at 1.2
miles per hour (1.93 kilometers/hour) or 130 drawbar horsepower at the
rated engine speed at a depth of 24 in. (61 cm). For burial depths
greater than 24 in. (61 cm), tractor manufacturers should be contacted
to determine minimum drawbar pull or drawbar horsepower requirements
necessary to achieve the specified burial depth.

**5.2** Plowing should be considered difficult when the equivalent of at
least 250 drawbar horsepower is applied to the plow. When difficulty in
plowing as defined above is encountered, alternative methods of placing
the cable or wire should be considered for those areas. The alternative
methods for placing the cable or wire in those areas could be the use of
aerial inserts, pre-ripping, rock trenching, or major re-routing of the
construction route. Since the 250 drawbar horsepower is considered to be
a very large amount of power, good judgement should be exercised to
prevent damage to the equipment and unnecessary or undue damage to the
terrain caused by the upheaval of large boulders.

**5.3** When a second tractor is needed to assist in the plowing
operation, the second tractor should be equipped with a winch and a
blade. The second tractor containing the winch and blade may then be
used for necessary R/W clearing and cleanup when it is not required to
assist the prime tractor.

**5.4** Compaction of plow slots should be performed after the cables or
wires have been plowed-in. The method of compacting most plow slots
should be as follows:

a\. Run the tractor track or tire along and immediately

adjacent to both sides of the plow slot;

b\. Fill in any ground depressions which may have developed

with soil to form a mound over the center of the plow

slot; and

c\. Then run the track or tire over the center slot.

**5.5** A signaling method between the person riding the reel tender or
plow, and the tractor operator should be developed to:

a\. Inform the tractor operator when the plow or reel

tender is to be stopped at access points along the

construction route;

b\. Prevent damage to the buried cables or wires; and

c\. Minimize the possibility of injury to construction

personnel.

The signaling method chosen should be able to attract the attention of
the tractor operator over the operating noise of the tractor. One such
method could be use of a loud alarm bell with a flashing light.

**6. HANDLING AND CARE OF MATERIALS DURING CONSTRUCTION**

**6.1** Extreme care should be exercised in handling materials during
the construction process. The plowing operation should be supervised at
all times to ensure that the cables or wires feed through the plow and
into the ground under zero tension. Under no circumstances should
tension be allowed to develop in the cables or wires. Whenever the plow
is stopped, sufficient lengths of cable or wire should be removed from
the reel to guard against sudden movements when the plow is restarted.

**6.2** Extreme caution should be exercised to ensure that the plow is
never backed up while the blade is in the ground. The backing up of the
plow could cause severe damage to the cables or wires. If the plow
strikes a buried object or rock during the plowing operation, the plow
should be stopped without backing up and the plow removed from the soil
and the cable or wire inspected for possible damage. Should it be
necessary to back up the plow, the cables or wires should be uncovered a
sufficient distance back from the plow and inspected for damage. If
cable or wire damage is discovered, the damage should be repaired in
accordance with the construction contract and specifications.

**6.3** Care should be exercised to prevent damage to exposed cables or
wires during the construction period. Construction work should be
scheduled to keep such exposure to a minimum. Where cables or wires are
being placed along the construction route, all trenching and backfilling
for both inline and short lateral trenches should be completed each day
so as not to leave the cables or wires exposed overnight. Cables or
wires left exposed are susceptible to damage. Cables or wires left
exposed are also considered hazards to vehicles, pedestrians, and
animals.

**6.4** Where outside plant housings are used, caution should be
exercised to avoid damaging the cables or wires when:

a\. Joining the lateral trenches to the plow slot;

b\. Installing the outside plant housings; and

c\. Forming the cables or wires in the outside plant

housings.

The stakes or stub poles of outside plant housings should be installed
before the cables or wires are placed in the lateral trenches.

**6.5** Cables or wires should be installed in outside plant housings as
soon as practicable. The installation work should be completed within
one week after the cables or wires have been plowed or trenched in the
ground. However, no trenches or other excavations should be left open
overnight unless the openings are protected by a method specified in the
contract.

**6.6** Buried plant connections using dissimilar metals should be
avoided to eliminate the possibility of galvanic corrosion. Therefore
buried plant connections should be made using only tinned coated metals.

**7. REPAIR OF CABLES OR WIRES DAMAGED DURING CONSTRUCTION**

**7.1** Minor damage to the outer jackets, where the shields or armors
of the cables or wires have not been bent, abraded, or penetrated should
be repaired in accordance with Bulletin

1753F-401(PC-2), RUS Standard for Splicing Copper and Fiber Optic
Cables.

**7.2** Where shields or armors have penetrated the outer jackets of
cables or wires, the damaged sections should be enclosed in direct
buried filled splice cases or outside plant housings. The outer jackets,
shields, or armors of the damaged sections should be removed as though
preparing for splicing. The shields or armors should then be bonded
together. Damage to the copper conductors or their insulations or
optical fibers or their buffer tubes should be repaired in accordance
with Bulletin

1753F-401(PC-2), RUS Standard for Splicing Copper and Fiber Optic
Cables.

**7.3** Cables or wires found to be damaged after installation should be
repaired. If the damage is considered minor, the damage should be
repaired in accordance with Bulletin

1753F-401(PC-2), RUS Standard for Splicing Copper and Fiber Optic
Cables. If the damage is considered major, the damage should be repaired
either by replacing the damaged sections with new cables or wires
spliced to the undamaged sections of the cables or wires or repaired in
accordance with the method specified in the contract.

**7.4** All outside plant housings or direct buried filled splice cases
added because of repairs should be numbered and shown on the
construction drawings. However, they should not be included in the final
inventory for compensation purposes as specified by the RUS 515 Contract
and RUS Bulletin 345-150 (RUS Form 515a).

**8. PREPARATION FOR SPLICING OR TERMINATION**

**8.1** Buried filled copper cables or wires should be spliced in
accordance with Bulletin 1753F-401(PC-2), RUS Standard for Splicing
Copper and Fiber Optic Cables and enclosed in RUS accepted or
technically accepted outside plant housings or direct buried filled
splice cases.

**8.2** Buried filled fiber optic cables should be spliced in accordance
with Bulletin 1753F-401(PC-2), RUS Standard for Splicing Copper and
Fiber Optic Cables and enclosed in RUS accepted or technically accepted
filled fiber optic splice cases. These splice cases should then enclosed
in either RUS accepted or technically accepted handholes or outside
plant housings specifically design for fiber optic systems.

**8.3** When terminal blocks are used in outside plant housings, only
RUS accepted or technically accepted filled terminal blocks should be
used.

**8.4** The front covers of Type \"H\" outside plant housings and the
dome covers of Type \"M\" outside plant housings should be bolted in the
closed position at the time the housings are installed. The covers of
both type outside plant housings should also be kept in closed position
at all times except when work is being performed within the outside
plant housings.

**9. INSTALLATION PROCEDURES FOR FILLED CABLES IN COLD WEATHER**

**9.1** Flexibility of filled copper cables or wires and filled fiber
optic cables should not be a problem at normal operating temperatures.
However, flexibility may be affected when the cables are exposed to
lower temperatures. The flexibility of filled copper cables or wires and
filled fiber optic cables could be sharply reduced at temperatures below
40°F (4.4°C). At temperatures below 40°F (4.4°C), almost twice the force
may be needed to bend the filled copper cables or wires and filled fiber
optic cables. Filled cables or wires and filled fiber optic cables
should be inspected each morning to determine if the cables or wires are
flexible enough for plowing when night time temperatures drop below 30°F
(-1.1°C). When filled cables or wires and filled fiber optic cables have
been stored outdoors and subjected to cold nights, considerable time may
be lost each morning waiting for the cables or wires to warm up even
though the day time temperature may be above 40°F (4.4°C). During the
spring and fall of the year, the filled copper cables or wires and
filled fiber optic cables may be stored in heated warehouses prior to
placement in the ground. This storage in heated warehouses allows the
filled copper cables or wires and filled fiber optic cables to be
transported to the project site as needed and installed while the cables
or wires are still flexible.

**9.2** Some filling compounds used in the cores of filled copper cables
or wires may become stiff as the temperature decreases making it
difficult to separate the cable or wire pairs. In general, filled copper
cable or wire installations below 40°F (4.4°C) could be slow, difficult,
and possibly even halted unless special precautions are taken to offset
the effects of the lower temperatures.

**9.3** Filling compounds used in loose tube buffers of filled fiber
optic cables should not become stiff as the temperature decreases. This
should allow the optical fibers to be easily separated at low
temperatures.

**9.4** As mentioned in Paragraph 9.2, the copper cable or wire pairs
may become difficult to separate as the temperature decreases. At
temperatures as low as 20°F (-6.7°C), the copper cable or wire pairs may
be separated by flexing the free ends of the cable or wire cores and
separating a few pairs at a time. It is also interesting to note that
the filling compounds at a temperature of 20°F (-6.7°C) are more user
friendly to work with than at elevated temperatures. Consequently, the
copper cable or wire pairs may be spliced without wiping the pairs free
of filling compound.

**10. ASSEMBLY UNITS**

**10.1** Detailed descriptions of all standard buried plant assembly
units are given in RUS Bulletin 345-150, Specifications and Drawings for
Construction of Direct Buried Plant (RUS Form 515a).

**10.2** Where standard buried plant assembly units are insufficient to
provide for unique buried plant construction requirements, detailed
\"nonstandard assembly units\" should be created to meet those
requirements. The buried plant nonstandard assembly units should be
approved by RUS prior to the bidding of the project.

**11. DIRECTIONAL BORING**

**11.1** Directional boring in buried plant construction should be
considered as an alternative method of installing cables or wires under
highways, streets, driveways, across lawns, etc., to avoid the expensive
costs of repairing and restoring the above mentioned items to their
pre-construction appearances.

**11.2** Directional boring should also be considered for installing
cables or wires under streams, lakes, or rivers, when in the opinion of
the borrower or borrower\'s resident engineer, the use of aerial inserts
are economically or environmentally cost prohibited.

**11.3** When directional boring is used in the buried construction
process, the installation should performed in accordance with boring
equipment manufacturer\'s recommendations.

**12. FIGURE EIGHTING CABLE**

**12.1** When \"figure eighting\" of cables or wires is required during
the buried construction process, the \"figure eighting\" of the cables
or wires should be performed either manually or mechanically.

**12.2** When performed manually, the cable or wire should be pulled off
the reel and \"figure eighted\" in a large open area free of
obstructions. The bend radius of the \"figure eight\" for copper cable
or wire should not be less than 10 times the cable\'s outside diameter.
For fiber optic cable, the \"figure eight\" bend radius should not be
less than 20 times the cable\'s outside diameter.

**12.3** When \"figure eighting\" is performed by a \"figure eighting\"
machine, the equipment manufacturer\'s instructions should be followed.

**13. AERIAL INSERTS**

**13.1** Aerial inserts in buried plant construction should be used over
streams and similar obstructions when, in the opinion of the borrower or
the borrower\'s resident engineer, cables or wires cannot be installed
either by plowing, trenching, directional boring, or protected by guard
assemblies. Every effort should be made to avoid using aerial inserts
because the aerial inserts are susceptible to storm damage and power
contacts. When aerial inserts are prone to possible contact with power
conductors operating at 300 volts or higher or there is a high
probability of lightning exposure to the aerial insert, fuse links
should be installed at both ends of the aerial insert. Fuse links should
consist of short lengths of color matched conductors that are at least
two (2) American Wire Gauge (AWG) sizes finer (numerically higher) than
the finest (numerically highest) gauge size of aerial and buried cables
or wires being installed.

**13.2** All assembly units such as poles, guys, anchors, etc., used for
the installation of aerial inserts in buried plant construction are
described in RUS Bulletin 345-153, Specifications and Drawings for
Construction of Pole Lines, Aerial Cables and Wires (RUS Form 515f).

**14. NUMBERING AND IDENTIFICATION**

**14.1** Every outside plant housing installed along the construction
route should be marked with route letters, housing numbers, warning
decals, and, when required, the load point numbers (when loaded lines
are determined by RUS to be economically feasible and the overall system
design complies with the Modernization Plan \[7 CFR 1751, Subpart B\]).

**14.2** Every direct buried filled splice case installed along the
construction route should be identified. The identification of the
direct buried filled splice cases should be accomplished by using either
above ground warning signs or electronic locating devices.

**15. ACCEPTANCE TESTING**

**15.1** After installation, buried copper cables or wires should be
tested in accordance with RUS Bulletin 345-63, RUS Standard for
Acceptance Tests and Measurements of Telephone Plant (PC-4) and the RUS
Form 515 Contract.

**15.2** After installation, buried fiber optic cables should be tested
in accordance with the procedures listed in the contract.