w. Courtesy of
Frank West, you can download these stan-
dards at www.underspace.com under the
White Papers heading.
Frank is a civilian GIS Specialist at Edwards
Air Force Base in California. He combines be-
ing the underground Utility Locate Lead with
the ongoing maintenance and updating of
Civil Engineering records. With a background
in urban planning and in data management
and collection in the USA and Europe, he has
a strong interest in the design and implemen-
tation of practical standards in the engineer-
ing and architectural fields.

Many non-metallic utility systems have an es-
timated 80-year life, but a locatable life that
ranges from zero to twenty years. Getting
more locating years out of a tracer system
involves proper construction and testing of
the wire. The reduction of avoidable utility
damages requires many things. One of them
is easier access to good information. Thanks,
Frank, for enabling Underground Focus to do
our job in providing this information.
Background
The primary focus of these design guidelines
is to ensure that the tracer wire installation
on underground utilities meets requirements
for the effective use of pipe and cable locat-
ing equipment. For best locating results over
the entire system, the tracer wire needs to
be continuous, insulated from the earth and
grounded on its ends. The weak links of any
tracer wire system are: the below-ground
connections, the end points and anywhere
the wire have become discontinuous due to
excavation damage.
The Wire
Tracer wire will be chosen appropriate to the
expected life of the utility, the soils corrosive
factors and the distance that a utility section
may need to be traced. Since the characteris-
tic electrical properties of the tracer wire will
at best remain constant (if not degrade from
a locating perspective), the choice of a tracer
wire has critical long-term implications.
The wire should have a minimum 12 AWG
size, constructed of solid copper and have a
minimum 30 mil polyethylene jacket designed
specifically for buried use. The quality of the
jacket should be appropriate to the degree of
soil moisture, contaminants and other known
potential corrosive effects limiting the effective
use of the wire as a conductor. The use of sol-
id copper wire type THHN or THWN VW-1
600 V, gasoline and oil resistant insulated is
the minimum requirement for tracer wire.
Since every tracer wire system installed should
have been designed to match the life of the
utility it accompanies, the major addressable
problem is immediate breakage caused by ex-
cavation. Therefore, consideration should be
given to utilizing 10 or 9 AWG size wire.
Installation in the Trench
Assuming that new utilities are placed at con-
ventional depths and spacing from other util-
ities, then the following design principles are
to be applied. Extreme depth or close packing
of utilities will require case-by-case applica-
tion of these general design principles and
may require extensive modifications.
The wire should not float somewhere in the
trench. The tracer wire will not be wrapped
around the pipe in a spiral as this is a source
of signal degradation and adds physical stress
to the wire. The wire will be placed on top of
the utility pipe and will be fastened in place at
approximately every 8 to 12 feet to secure it in
place when the trench is backfilled. Metallic
fasteners are not to be used. The wire on fuel
pipelines and on gas lines will not be fastened
to the top of the pipe. Instead, the wire will be
fastened to the pipe with the use of a spacer to
keep the wire at a set distance from the pipe.
The wire will be allowed some slack to allow
for bends in laying and for future installation
of joints, splices, tapping saddles, etc. The
slack should also be sufficient to allow for
small earth movements occurring in compact-
ing trench fill or through natural subsidence.
If it is necessary to join the tracer wire be-
low ground, the wire should be joined in a
permanent bond (braising, cad welding or
equivalent) and the joined area insulated and
rendered watertight in order to prevent cor-
rosion. Where the cable is designed specifi-
cally for use as tracer wire, the corresponding
connectors should be used.

Installation of Tracer Wire
Access

Points
Any tracer wire system will be accessible at a
minimum of two points, the beginning and
the end of the wire. (Exceptions to this, see
section on: Termination of Tracer Wire). In
practice, there will usually be multiple points
of access.
The general design of access points to tracer
wire is that the wire will be brought to ground
level and a connection point provided for a
locator to clip equipment onto the wire. In
the simplest case, the wire is brought up a
valve box tube as a continuous loop that ex-
tends three feet above ground. The loop is
coiled and placed in the valve box tube. The
UF
loop preserves the continuity of the line, and
the loop of wire is reasonably accessible at the
top of the valve tube. Use of the valve by the
utility owner can be achieved by first pulling
the wire out, then using a valve key. If the
contractor laying the new utility needs to join
sections of tracer wire, these access points are
considered an above ground join and do not
need to be extensively insulated. Split bolts
(preferred) and wire nuts are options. The
join can be taped.
Tracer wires in valve boxes are vulnerable to
being twisted around valve keys and snapped,
or pushed to the bottom of the valve box
where they are out of reach and inaccessible
to the locator. The problem can be mitigated
by correctly installing the tracer wire so it en-
ters the valve box near the top where it can be
coiled just under the valve cap. This way the
utility worker can easily pull the loop out of
the way before using the valve.
Distance between Access Points
Access to tracer wire will in general be at every
point the utility has another physical access
point. On water, gas and fuel lines all valves
below ground are considered access points
and tracer wire should be accessible at these
points. Access points distance from each other
will thus vary from a few feet up to hundreds
of feet depending on the utility and the proj-
ect. Concentrations of multiple valves on one
utility within 10 feet of each other may be sim-
plified to one access point if this is made ex-
plicit in the tracer wire submission drawings.
There normally should be an access point at
least every 500 feet. On long utility runs that
exceed 500 feet there should be an interme-
diate access point provided by bringing the
tracer wire to the ground level and install-
ing an above ground accessible junction box.
Where this is a problem the tracer wire sys-
tem may be initially designed with cable that
can be demonstrated to carry an adequate
signal over longer distances.
Termination of Tracer Wire
The beginning and end of a tracer wire are
equally logical places to be brought to the
surface. Above ground tracer wire termina-
tion points will be clearly tagged or labeled as
end points. If possible, an as-built point-to-
point wiring diagram will be provided and
mounted next to the termination point.
The end points of any tracer wire system are
also suitable points to place anodes. Anodes
have the dual function of providing cathodic
protection for the tracer wire (thus increas-
ing its life expectancy) and for providing high
quality ground points.
Where a new non-metallic utility line taps
into an existing metal utility line, the tracer
wire should be either terminated at an anode
next to the metallic utility or be permanently
attached to the metallic line. A tracer wire
will not be terminated to or on another tracer
wire or metallic utility line unless the two
systems are demonstrably compatible. This is
to reduce the potential for rapid corrosion of
one system due to a reverse cathodic effect.
Lateral connections will be designed to be
compatible with the tracer wire on the main
line. If the termination of the lateral at the
main line tracer wire is underground, the join
will meet all requirements for underground
joins applicable to the main line tracer wire. If
the join is above ground, e.g. at a valve for the
lateral line, the joint will be a permanent one
(split bolt or better) to the main line tracer
wire and will be accessible.
Where the lateral line effectively terminates/
interfaces with a building, the lateral tracer
line section will be
terminated in an
appropriate manner
for the utility. Where
the utility enters a
meter, junction box
or similar point out-
side the building, the
tracer wire should
be brought to the
surface and termi-
nated by attaching
it to the appropriate
utility with a suit-
able fastener so that
it is clearly visible as
part of the utility in-
stallation (no dan-
gling wires). When
the utility access is
only available inside
the building, the
tracer wire