Page 73 - Pipeline Risk Management Manual Ideas, Techniques, and Resources

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training to the construction community, conduct publicity campaigns from the use ofa detection device (with verification by physical
to educate the public to excavation notification requirements, and probing by experienced personnel) to merely sighting between
work with facility operators to protect their underground facilities. aboveground facilities (a method that often leads to errors).
Other centers do little work in these areas. Some pipe materials, such as plastic, are difficult to locate
Some centers use positive response procedures-members who do
not mark facilities in the construction area [instead] confirm with the when buried, and some sites require expensive excavations to
excavators that they have no facilities in the area rather than just not mark precisely locate the line, regardless ofthe material. Some mate-
a location; other centers do not have this requirement. A part ofthe Miss rials are also susceptible to damage by the common probing
Utility program in the Richmond Virginia, area uses positive response techniques used to locate the line.
procedures to notify the excavator when the marking is complete. Especially in congested areas, the need to determine the
Facility owners directly inform a voice messaging system ofthe status of exact location of the pipeline is critical. Modern locating tech-
a notification ticket. As a time-saving alternative, the contractor can call niques include instrumentation that can detect buried pipe via
the information system anytime to receive an up-to-date status of their electromagnetic signals, impressed electric signals, and ground
marking request. Information indicating that marking has been com- penetrating radar. These instruments are designed to determine
pleted or that no facilities are located in the area of excavation, allows
construction work to proceed as soon as marking is completed rather line location and depth. Because they are susceptible to extra-
than waiting the full time period for which marking activity is allowed. neous signals and barriers to signal reception, a degree of oper-
The important elements of an effective one-call notification center ator skill is required. For a variety of situation-specific
have been generally identified by industry organizations. For exam- reasons-such as pipe material, type of cover, and presence of
ple, the position ofthe Associated General Contractors ofAmerica on interfering signals-not all pipelines can be located with this
one-call systems is summarized in six elements: instrumentation. In some cases, special wires are inserted into
non-conducting pipe materials to aid in line location. These
Mandatory participation tracer wires or locator wires are susceptible to damage from
Statewide coverage corrosion, lightning surges, and external forces. Another aid to
48-hour marking response
Standard marking requirements pipeline location is the installation of small electronic markers
Continuing education that emit discrete radio-frequency (RF) signals when polled by
Fair system ofliahility. surface instrumentation [66].
Line locating can also be accomplished by direct excavation
Participants at the Safety Board’s 1994 workshop, on the other hand andor probing (also called prodding) using a stiff rod to pene-
developed detailed lists of elements they believed are essential for an trate the ground, sometimes with a water-jet assist, and physi-
effective one-call notification center, other elements a center should cally contact the top of the pipe. With some pipe materials and
have, and elements it could have. All agreed, however, that first and
foremost was the need for mandatory participation and use ofnotifica- coatings, these latter methods risk damage to the pipeline.
tion centers hy all parties. The Safety Board concludes that many Some common methods of line locating are listed in Table 3.1.
essential elements and activities of a one-call notification center have Practices for marking the underground facilities can have an
been identified but have not been uniformly implemented. [64] impact on the risk of excavation damage. Good practices
include pre-marking of the intended excavation site by the
The last scoring item deals with the pipeline company’s excavator to clearly identify to the facility owner the area of
response to a report of third-party excavation activity. digging; positive response by the utility owner to confirm that
Obviously, reports that are not properly addressed in a timely underground facilities have been marked or to verify that no
manner negate the effects of reporting. The evaluator should marking was necessary; the use of industry-accepted marking
look for evidence that all reports are investigated in a timely standards to unambiguously communicate the type of facility
manner. A sense of professionalism and urgency should exist and its location; marking facility locations within the specified
among the responders. Appropriate response may include notification time; and responding to requests for emergency
markings, when necessary. The time frame for excavation
A system to receive and record notification of planned exca- marking is usually specified by state damage prevention laws.
vation activity Twenty states require underground facility marking to be
Dispatching ofpersonnel to the site to provide detailed mark- accomplished within 48 hours of excavation notification [64].
ers of pipeline location Some pipes that are difficult to locate from the surface
Comprehensive marking and locating procedures and training require expensive excavations to determine their precise loca-
Accurate maps and records showing pipeline locations, tion. This is often the case for lines located beneath concrete
depths, and specifications sidewalks or roadways and those adjacent to buildings. For
Prejob communications or meetings with the excavators these reasons, modern distribution systems often rely heavily
On-site inspection during the excavation on accurate records and drawings to show exact piping loca-
A system to ensure updating of drawings tions. This allows for more potential human error, as is dis-
Inspection of the pipeline facilities after the excavation. cussed in the incorrect operations index discussion (Chapter 6).
The use of standard marking colors informs the excavator
The evaluator may look for documentation or other evidence about the type of underground facility for which the location
to satisfy himself that an appropriate number of these often crit- has been marked (Table 3.2). Markings of the appropriate color
ical actions is being taken. for each facility are placed directly over the centerline of the
pipe, conduit, cable, or other feature.
Locating and marking methods Offset marking procedures are used when direct marking
cannot be accomplished. For most surfaces, including paved
In awarding points, the evaluator may wish to distinguish surfaces, spray paint is used for markings; however, stakes or
between methods of direct line location. Methods may range flags may be used if necessary. A proposed marking standard