[Guidelines for the installation and operation of]{.underline}

# Irrigation systems near high voltage transmission lines

[Bonneville power administration]{.underline}

[Transmission Maintenance]{.underline}

[&]{.underline}

[Electrical Effects]{.underline}

# TNLD

February 15, 2002

This guideline is intended to assist the public in planning and
installing irrigation systems near BPA transmission lines. It is also
intended for use by BPA employees in answering questions from the
public, reviewing applications for right-of-way use, and for locating
transmission lines in irrigated areas. Information in this guide is
intended only as general guidelines.

Irrigation systems fall into two categories: fixed and mobile. Fixed
irrigation systems include the fixed pipe-type systems and the row and
rill-type systems. Mobile systems, which have gained in popularity, can
be broken down into roughly four types: pipe-type, wheel-type, circular
irrigation system, and high volume, high velocity systems. Each of the
types has its own characteristics which the installer and operator
should be aware of when working adjacent to high voltage transmission
lines. For each type of system, installation suggestions and safe
working practices near high voltage transmission lines will be
presented.

I. [FIXED-TYPE SYSTEMS]{.underline}

### Pipe-Type and Row and Rill-Type

Fixed pipe-type irrigation systems are used for long term watering of
landscaping, such as golf courses and playing fields, or crops such as
orchards and vineyards. The irrigation piping is usually installed
underground, and sprinkler heads are permanently or temporarily
connected to the feed piping by risers of various lengths. The length of
a riser depends on the type of vegetation and the purpose for the
sprinkling. The row and rill-type of irrigation uses long trenches dug
in the surface of the soil, and fed by gates, valves, or siphon tubes
installed in a canal or ditch at the head of each trench.

## Installation Suggestions

Equipment used to install fixed-type irrigation systems should never be
closer than the minimum distance to transmission line conductors as
shown on Table I (page 11). The sprinkler heads should be located so
that they never spray water on the transmission line conductors. All
underground water supply piping crossing BPA right-of--way should do so
at an angle of not less than 60 degrees to the centerline of the
transmission lines. It should be buried, whenever possible, a minimum of
24 inches underground, and should be marked, when practical, where it
enters and leaves the right-of-way and at all angle points within the
right-of way. These last two conditions will prevent damage to the
piping due to movement of heavy equipment on the right-of way.

All metal pipelines, above or below ground, should be kept 50 feet (15
m) from any part of a BPA structure, and 15 feet (5 m) from any
grounding system.

Any movement of earth on a transmission line right-of-way which might
reduce the stability of a transmission tower or pole or would
permanently decrease the conductor to ground distance, shall not be
allowed unless approved by the appropriate BPA area office.

## Safe Working Practices

The fixed pipe-type sprinkler systems are always in contact with the
ground. There is very little chance of feeling even a small electrical
shock while contacting one of these systems, which is close to a
transmission line. Care must be exercised when installing and removing
the riser pipes so that an adequate distance is maintained between the
overhead conductors and the riser pipes. The recommended minimum
distances are shown on Table I (page 11).

II\. [MOBILE SYSTEMS]{.underline}

#### Pipe-Type Systems

Mobile pipe-type irrigation systems are assembled, disassembled, and
moved by hand. The pipes in these systems are laid on the surface of the
ground and the water supply is usually connected to the irrigation
system through valves in a header pipe. The header pipe is often located
at one side of the field, and taps are located in the header pipe at
convenient intervals so that moving the pipe from one tap to another
assures coverage of the whole field. Sprinkler heads are installed along
the irrigation piping and apply water to circular areas, the diameters
of which are governed by the nozzle size and water pressures.

[Installation Suggestions]{.underline}

Equipment used to install mobile systems should never be closer than the
minimum distance to transmission line conductors as shown on Table I
(page 11). All underground water supply piping crossing BPA right-of-way
should do so at an angle of not less than 60 degrees to the centerline
of the transmission lines. It should be buried, whenever possible, a
minimum of 24 inches underground, and should be marked, when practical,
where it enters and leaves the right-of-way and all angle points within
the right-of-way. These last two conditions will prevent damage to the
piping due to movement of heavy equipment on the right-of-way.

All metal pipelines, above or below ground, should be kept 50 feet (15
m) from any part of a structure, and 15 feet (5 m) from any grounding
system.

Any movement of earth on a transmission line right-of-way which might
reduce the stability of a transmission tower or pole or would
permanently decrease the conductor to ground distance, shall not be
allowed unless approved by the appropriate BPA area office.

[Safe Working Practices]{.underline}

Because this type of system is laid on the ground surface when
operating, the chance of feeling even a small shock when picking up a
length of pipe that was lying under or near a transmission line is
unlikely.

[A person carrying a length of pipe from one location to another should
always carry the pipe in the horizontal position, especially while
crossing under any power line. Standing pipe on end to remove dirt or
small animals should never be done before a careful check has been made
to see if the pipe could come close to any overhead lines.]{.underline}
After carrying a pipe section under the transmission line to a new setup
point, the operator may experience a nuisance shock when he touches the
header pipe if the ground is very dry. A slight shock may also be felt
if a piece of pipe is being unloaded from a rubber-tired vehicle located
near a transmission line.

[The likelihood of shocks and incidents of contacts between upended
pipes and power lines can be greatly reduced if the pipe is never
unloaded under the transmission line.]{.underline} A distance of more
than 50 feet (15 m) from the centerline of the transmission line is
recommended for unloading the pipe. If very dry soil conditions exist,
such as at the beginning of the irrigating season, connecting the first
length of pipe to the head pipe and proceeding by connecting short
lengths to the first is a good practice especially when within 50 feet
(15 m) of the transmission line centerline.

A.  [Wheel-Type Systems]{.underline}

Wheel-type systems are very similar to the pipe-type system previously
addressed (i.e., a long straight length of 4-5 inch (10-13 cm) pipe
equipped with distributed sprinkler heads). However, in this case,
instead of the pipe being disassembled to be moved, it is rolled down
the field on 4-5 foot (1.2-1.5 m) diameter wheels (usually metal). The
pipe actually forms the axle for the group of wheels supporting it. In
this case, the pipe is suspended 2-2.5 feet (60-80 cm) off the ground
(see Fig. 1, page 8). The motive power can either be manpower for short
lengths or a power unit for long lengths. The power unit is usually
located close to the center of the pipe run.

[Installation Suggestions]{.underline}

When possible, the system should be installed with its length
perpendicular to the transmission line. Equipment used to install
wheel-type systems should never be closer than the minimum distance to
transmission line conductors as shown on Table I (page 11). All
underground water supply piping crossing BPA right-of-way should do so
at an angle of not less than 60 degrees to the centerline of the
transmission lines. It should be buried, whenever possible, a minimum of
24 inches underground, and should be marked, when practical, where it
enters and leaves the right-of-way and at all angle points within the
right-of-way. These last two conditions will prevent damage to the
piping due to movement of heavy equipment on the right--of-way.

All metal pipelines, above or below ground, should be kept 50 feet (15
m) from any part of a BPA structure and 15 feet (5 m) from any grounding
system.

Any movement of earth on a transmission line right-of--way which might
reduce the stability of a transmission tower or pole or would
permanently decrease the conductor to ground distance, shall not be
allowed unless approved by the appropriate BPA area office.

[Safe Working Practice]{.underline}

When a wheel-type system is to be operated near or under a transmission
line, the assembling of the system should follow the same procedure as
mentioned for pipe-type systems. In many cases, the wheel-type system
will be operated with its length parallel to the transmission lines. For
wet soil conditions and because of the good ground contact through at
least one or two of the metal wheels, very few shock sensations will be
experienced when touching the pipe. A simple precaution should be
observed during dry soil conditions when the long system is being
connected to header pipe valves within 50 feet (15 m) of the centerline
of the transmission line.

Under these conditions, the operator should connect the pipe to the
valve with a short length of wire equipped with a clamp on each end (see
Fig. 1, page 8). This will effectively drain off any accumulated charge
on the irrigation pipe. This wire connection should be made to the
header pipe valve connecting the irrigation pipe.

B.  [Circular Irrigation Systems]{.underline}

This system consists of water pipe held above ground with sprinkler
heads distributed along its length (see Fig. 2, page 9). The system is
often 1/4 mile (400 m) long and pivots around a center point, which is
the water source. The pipe is carried on motor-propelled supports spaced
along the pipe. Rotation of the system irrigates a circular area or with
special equipment, odd-shaped areas. The system will not cover a
360-degree rotation when an obstruction such as a transmission line
structure intersects the pattern. For these cases, reversing travel to
avoid obstructions or a special guidance system is used. Unlike the
wheel system, the circular system is rarely disconnected from the source
point, except for periodic maintenance.

[Installation Suggestions]{.underline}

Equipment used to install circular irrigation systems should never be
closer than the minimum distance to transmission line conductors as
shown on Table I (page 11). All underground water supply piping,
electric power cables, and communication cables crossing BPA
right-of-way should do so at an angle of not less than 60 degrees to-the
centerline of the transmission lines. It should be buried, whenever
possible, a minimum of 24 inches underground, and should be marked, when
practical, where it enters and leaves the right-of-way and at all angle
points within the right-of-way. These last two conditions will prevent
damage to the piping and cables due to movement of heavy equipment on
the right-of-way.

All metal pipelines, pivots, electrical power cables, and communication
cables, above or below ground, should be kept 50 feet (15 m) from any
part of a BPA structure and 15 feet (5 m) from any grounding system. The
center point or pivot point of the irrigation system should be located
20 feet (6.5 m) laterally outside the outermost conductor.

Any movement of earth on a transmission line right-of-way which might
reduce the stability of a transmission tower or pole or would
permanently decrease the conductor to ground distance, shall not be
allowed unless approved by the appropriate BPA area office.

Nozzles should be positioned so that they do not spray water on the
transmission line conductors. When this is not practical, distances
given in Table II (page 12) should be used between nozzle and centerline
of the transmission line. The circular irrigation system should be
installed so that the minimum distance given in Table I (page 11) is
maintained between conductors and sprinkler system hardware. All nozzle
risers, which pass under a transmission line, should be equipped with
spoilers or automatic shut-offs in case a nozzle breaks or drops off.
This will insure that that a solid stream of water is not projected into
the transmission line.

[Safe Working Practices]{.underline}

If the pivot point of a circular irrigation system is near or under a
transmission line, the irrigation system could acquire an electrostatic
charge during operation. To prevent this electrostatic charge buildup,
the pivot point should provide a good electrical ground for the
sprinkler system. This will eliminate electrostatic shock nuisances
during operation.

This electrical ground, however, does not eliminate hazards due to
inductive coupling between the transmission line and the sprinkler pipe.
With the irrigation system near or under a transmission lines, the pipe
could rotate to two locations parallel or nearly parallel to the
transmission line. This situation is similar to the position of the
wheel-type system in Fig. 1, page 8.

[It is recommended that personnel not touch the sprinkler pipe or its
supporting structures when the system is operating under or parallel to
and near a transmission line.]{.underline}

The pipe used in circular irrigation systems is larger, higher off the
ground, and generally longer than wheel-type systems. Also, the driving
wheels are usually rubber-tired and under dry conditions, could insulate
the pipe from ground. With the sprinkler pipe parallel and close or
under the transmission line, the inductive coupling between the
transmission line and the sprinkler boom can result in hazardous shock
currents if a person touches the system while the boom is connected to
the pivot point. For these reasons, [any maintenance work should be done
with the sprinkler pipe perpendicular to the transmission
lines.]{.underline} This situation is illustrated in Fig. 2, page 9.
[When this is not practical, the ends of the pipe should be electrically
grounded (connected to or in contact with earth) before beginning
maintenance work and each disjoined length of the system should be
individually grounded on both sides of the coupling before it is
decoupled.]{.underline} Metallic ground rods are recommended for this
grounding procedure.

C.  [High Volume, High Velocity Systems]{.underline}

These systems use large high-pressure nozzles to sprinkle large areas.
The Vermeer mobile irrigator is an example of this type of system (see
Fig. 3, page 10). High velocity, high volume nozzles are located at each
end of two arms approximately 70 feet (21 m) in length. The arms rotate
due to discharge of water through the nozzles. They rotate on a base
attached to a small chassis, which can be towed or pushed to different
points in the field. Nozzle diameters normally vary from 3/4 inch (2 cm)
to 1 15/16 inch (5 cm). Water pressures used are in the range of 80-100
psi. The nozzles discharge a high velocity solid stream of water from
the ends of the arms. The water stream may reach a height of 30-35 feet
(9-11 m), and may be projected as much as 200 feet (60 m) horizontally.
Other systems using single nozzles (water cannons) with clapper have
similar characteristics.

[Installation Suggestions]{.underline}

Maintaining an adequate distance between the irrigation equipment and
transmission line conductors is essential for safe operation of these
types of systems. The irrigation equipment should be positioned so that
water is not projected into transmission line conductors. When this is
not practical, distances given in Table II (page 12) should be used
between nozzle and centerline of the transmission line. The irrigation
systems should be located so that the recommended minimum distance given
in Table I (page 11) are maintained between the conductors and the
sprinkler system hardware. All underground water supply piping crossing
BPA right-of-way should do so at an angle of not less than 60 degrees to
the centerline of the transmission lines. It should be buried, whenever
possible, a minimum of 24 inches underground, and should be marked, when
practical, where it enters and leaves the right-of-way and at all angle
points within the right-of-way. These conditions will prevent damage to
the piping due to movement of heavy equipment on the right-of-way.

All metal pipelines, above or below ground, should be kept 50 feet (15
m) from any part of a BPA structure and 15 feet (5 m) from any grounding
system.

Any movement of earth on a transmission line right-of-way which might
reduce the stability of a transmission tower or pole or would
permanently decrease the conductor to ground distance, shall not be
allowed unless approved by the appropriate BPA area office.

[Safe Working Practices]{.underline}

Great caution should be exercised when moving these types of systems
under transmission lines. The small wheel bases tend to be unstable on
rough ground and could cause the equipment to swing off balance lifting
a piece of the system into the overhead conductors. If mobile surface
piping is used for supply, a person carrying a length of pipe from one
location to another should always carry the pipe in a horizontal
position especially while crossing under any power line. Standing the
pipe on end to remove dirt or small animals should never be done before
a careful check has been made to see if the pipe could come close to any
overhead lines.

II\. [NOTE]{.underline}

This document is the result of editing and modifications of the original
document "Guidelines for the Installation and Operation of Irrigation
Systems near High Voltage Transmission Lines," February 21, 1978,
authored by D.J. Nichols.

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##### TABLE I

###### RECOMMENDED MINIMUM DISTANCES BETWEEN

**EQUIPMENT AND TRANSMISSION LINE CONDUCTORS**

  ---------------------------- ---------------- --------------------------
  TRANSMISSION LINE VOLTAGE    DISTANCE BETWEEN 
                               CONDUCTOR AND    
                               EQUIPMENT        

                               FEET             METERS

  287 KV AC and below          15               4.6

  345 KV AC                    16               4.9

  500 KV AC                    20               6.1

  **±** 400 KV DC              17               5.2

  **±** 500 KV DC              21               6.4
  ---------------------------- ---------------- --------------------------

**NOTE: NEVER PHYSICALLY MEASURE THESE**

**DISTANCES WITH DEVICES SUCH AS**

**TAPE MEASURES, POLES, ETC.**

**TABLE II**

**RECOMMENDED MINIMUM DISTANCES**

**BETWEEN HIGH PRESSURE IRRIGATION NOZZLES AND**

**HIGH VOLTAGE TRANSMISSION LINES**

  ------------- --------- -------------- -------- -------- -------- -------- -------- --------- -------- --------- -------- --------- --------
  **SPRINKLER             **HORIZONTAL                                                                                                
  NOZZLE                  DISTANCE                                                                                                    
  DIAMETER**              NOZZLE TO                                                                                                   
                          CENTER LINE OF                                                                                              
                          POWER LINE**                                                                                                

                          **115 KV AC             **230 KV          **345 KV          **500 KV           **±400 KV          **±500 KV 
                          LINE**                  AC                AC                AC LINE**          DC LINE**          DC LINE** 
                                                  LINE**            LINE**                                                            

  **in.**       **cm.**   **ft.**        **m.**   ft.      **m.**   ft.      **m.**   **ft.**   **m.**   **ft.**   **m.**   **ft.**   **m.**

  1/4           0.635     29             8.8      43       13.0     51       15.4     61        18.4     40        12.2     50        15.2

  3/8           0.952     37             11.1     51       15.5     63       19.0     73        22.2     42        12.8     54        16.4

  1/2           1.270     44             13.1     60       18.1     68       20.5     82        24.8     53        16.1     67        20.3

  5/8           1.587     51             15.5     69       20.8     80       24.2     92        27.9     65        19.7     79        24.1

  3/4           1.905     53             16.1     73       22.2     87       26.5     106       32.3     80        24.4     100       30.2

  7/8           2.222     68             20.7     84       25.6     97       29.6     106       32.3     80        24.4     100       30.2

  1             2.540     68             20.7     89       27.1     97       29.6     111       33.8     87        26.4     107       32.5

  1 1/8         2.857     84             25.6     104      31.7     118      36.0     132       40.2     110       33.5     136       41.2

  1 3/8         3.492     89             27.1     109      33.2     123      37.5     137       41.7     115       35.0     142       43.1

  1 5/8         4.127     99             30.2     125      38.1     138      42.1     157       47.8     138       41.9     169       51.5

  1 15/16       4.928     124            37.8     150      45.7     164      50.0     182       55.5     166       50.6     204       62.3
  ------------- --------- -------------- -------- -------- -------- -------- -------- --------- -------- --------- -------- --------- --------